From 939539f6c5f0c1562c2ba784e2926d4e9520a7a4 Mon Sep 17 00:00:00 2001
From: Yury-Fridlyand <yuryf@bitquilltech.com>
Date: Thu, 6 Oct 2022 20:27:29 -0700
Subject: [PATCH 01/14] Add functions `ADDTIME` and `SUBTIME`.

Signed-off-by: Yury-Fridlyand <yuryf@bitquilltech.com>
---
 .../expression/datetime/DateTimeFunction.java | 144 +++++++-----------
 .../expression/datetime/DateTimeTestBase.java |  28 +++-
 docs/user/dql/functions.rst                   | 121 ++-------------
 docs/user/ppl/functions/datetime.rst          | 115 ++------------
 .../sql/sql/DateTimeFunctionIT.java           |  19 ---
 ppl/src/main/antlr/OpenSearchPPLParser.g4     |  58 ++-----
 sql/src/main/antlr/OpenSearchSQLParser.g4     |   9 ++
 7 files changed, 126 insertions(+), 368 deletions(-)

diff --git a/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java b/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
index df4dd0a96b5..f33534801e6 100644
--- a/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
+++ b/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
@@ -128,7 +128,6 @@ public void register(BuiltinFunctionRepository repository) {
     repository.register(second());
     repository.register(subdate());
     repository.register(subtime());
-    repository.register(sysdate());
     repository.register(time());
     repository.register(time_to_sec());
     repository.register(timestamp());
@@ -250,38 +249,22 @@ private DefaultFunctionResolver adddate() {
    */
   private DefaultFunctionResolver addtime() {
     return define(BuiltinFunctionName.ADDTIME.getName(),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
-            TIME, TIME, TIME),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
-            TIME, TIME, DATE),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
-            TIME, TIME, DATETIME),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
-            TIME, TIME, TIMESTAMP),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
-            DATETIME, DATETIME, TIME),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
-            DATETIME, DATETIME, DATE),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
-            DATETIME, DATETIME, DATETIME),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
-            DATETIME, DATETIME, TIMESTAMP),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
-            DATETIME, DATE, TIME),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
-            DATETIME, DATE, DATE),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
-            DATETIME, DATE, DATETIME),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
-            DATETIME, DATE, TIMESTAMP),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
-            DATETIME, TIMESTAMP, TIME),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
-            DATETIME, TIMESTAMP, DATE),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
-            DATETIME, TIMESTAMP, DATETIME),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
-            DATETIME, TIMESTAMP, TIMESTAMP)
+        impl(nullMissingHandling(DateTimeFunction::exprAddTime), TIME, TIME, TIME),
+        impl(nullMissingHandling(DateTimeFunction::exprAddTime), TIME, TIME, DATE),
+        impl(nullMissingHandling(DateTimeFunction::exprAddTime), TIME, TIME, DATETIME),
+        impl(nullMissingHandling(DateTimeFunction::exprAddTime), TIME, TIME, TIMESTAMP),
+        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, DATETIME, TIME),
+        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, DATETIME, DATE),
+        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, DATETIME, DATETIME),
+        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, DATETIME, TIMESTAMP),
+        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, DATE, TIME),
+        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, DATE, DATE),
+        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, DATE, DATETIME),
+        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, DATE, TIMESTAMP),
+        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, TIMESTAMP, TIME),
+        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, TIMESTAMP, DATE),
+        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, TIMESTAMP, DATETIME),
+        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, TIMESTAMP, TIMESTAMP)
     );
   }
 
@@ -568,38 +551,22 @@ private DefaultFunctionResolver subdate() {
    */
   private DefaultFunctionResolver subtime() {
     return define(BuiltinFunctionName.SUBTIME.getName(),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
-            TIME, TIME, TIME),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
-            TIME, TIME, DATE),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
-            TIME, TIME, DATETIME),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
-            TIME, TIME, TIMESTAMP),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
-            DATETIME, DATETIME, TIME),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
-            DATETIME, DATETIME, DATE),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
-            DATETIME, DATETIME, DATETIME),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
-            DATETIME, DATETIME, TIMESTAMP),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
-            DATETIME, DATE, TIME),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
-            DATETIME, DATE, DATE),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
-            DATETIME, DATE, DATETIME),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
-            DATETIME, DATE, TIMESTAMP),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
-            DATETIME, TIMESTAMP, TIME),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
-            DATETIME, TIMESTAMP, DATE),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
-            DATETIME, TIMESTAMP, DATETIME),
-        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
-            DATETIME, TIMESTAMP, TIMESTAMP)
+        impl(nullMissingHandling(DateTimeFunction::exprSubTime), TIME, TIME, TIME),
+        impl(nullMissingHandling(DateTimeFunction::exprSubTime), TIME, TIME, DATE),
+        impl(nullMissingHandling(DateTimeFunction::exprSubTime), TIME, TIME, DATETIME),
+        impl(nullMissingHandling(DateTimeFunction::exprSubTime), TIME, TIME, TIMESTAMP),
+        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, DATETIME, TIME),
+        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, DATETIME, DATE),
+        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, DATETIME, DATETIME),
+        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, DATETIME, TIMESTAMP),
+        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, DATE, TIME),
+        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, DATE, DATE),
+        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, DATE, DATETIME),
+        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, DATE, TIMESTAMP),
+        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, TIMESTAMP, TIME),
+        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, TIMESTAMP, DATE),
+        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, TIMESTAMP, DATETIME),
+        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, TIMESTAMP, TIMESTAMP)
     );
   }
 
@@ -742,34 +709,34 @@ private ExprValue exprAddDateDays(ExprValue date, ExprValue days) {
   /**
    * Adds or subtracts time to/from date and returns the result.
    *
-   * @param functionProperties A FunctionProperties object.
-   * @param temporal A Date/Time/Datetime/Timestamp value to change.
-   * @param temporalDelta A Date/Time/Datetime/Timestamp object to add/subtract time from.
-   * @param isAdd A flag: true to add, false to subtract.
+   * @param date A Date/Time/Datetime/Timestamp value to change.
+   * @param time A Date/Time/Datetime/Timestamp object to add/subtract time from.
+   * @param add A flag: true to add, false to subtract.
    * @return A value calculated.
    */
-  private ExprValue exprApplyTime(FunctionProperties functionProperties,
-                                  ExprValue temporal, ExprValue temporalDelta, Boolean isAdd) {
-    var interval = Duration.between(LocalTime.MIN, temporalDelta.timeValue());
-    var result = isAdd
-        ? extractDateTime(temporal, functionProperties).plus(interval)
-        : extractDateTime(temporal, functionProperties).minus(interval);
-    return temporal.type() == TIME
-        ? new ExprTimeValue(result.toLocalTime())
-        : new ExprDatetimeValue(result);
+  private ExprValue exprApplyTime(ExprValue date, ExprValue time, Boolean add) {
+    var timeToAdd = time.type() == TIME
+        ? time.timeValue()
+        : time.datetimeValue().toLocalTime();
+    var dt = date.type() == TIME
+        ? LocalDate.now().atTime(date.timeValue())
+        : date.datetimeValue();
+    var interval = Duration.between(LocalTime.MIN, timeToAdd);
+    dt = add ? dt.plus(interval) : dt.minus(interval);
+    return date.type() == TIME
+        ? new ExprTimeValue(dt.toLocalTime())
+        : new ExprDatetimeValue(dt);
   }
 
   /**
    * Adds time to date and returns the result.
    *
-   * @param functionProperties A FunctionProperties object.
-   * @param temporal A Date/Time/Datetime/Timestamp value to change.
-   * @param temporalDelta A Date/Time/Datetime/Timestamp object to add time from.
+   * @param date A Date/Time/Datetime/Timestamp value to change.
+   * @param time A Date/Time/Datetime/Timestamp object to add time from.
    * @return A value calculated.
    */
-  private ExprValue exprAddTime(FunctionProperties functionProperties,
-                                ExprValue temporal, ExprValue temporalDelta) {
-    return exprApplyTime(functionProperties, temporal, temporalDelta, true);
+  private ExprValue exprAddTime(ExprValue date, ExprValue time) {
+    return exprApplyTime(date, time, true);
   }
 
   /**
@@ -1159,13 +1126,12 @@ private ExprValue exprSubDateInterval(ExprValue date, ExprValue expr) {
   /**
    * Subtracts expr2 from expr1 and returns the result.
    *
-   * @param temporal A Date/Time/Datetime/Timestamp value to change.
-   * @param temporalDelta A Date/Time/Datetime/Timestamp to subtract time from.
+   * @param date A Date/Time/Datetime/Timestamp value to change.
+   * @param time A Date/Time/Datetime/Timestamp to subtract time from.
    * @return A value calculated.
    */
-  private ExprValue exprSubTime(FunctionProperties functionProperties,
-                                ExprValue temporal, ExprValue temporalDelta) {
-    return exprApplyTime(functionProperties, temporal, temporalDelta, false);
+  private ExprValue exprSubTime(ExprValue date, ExprValue time) {
+    return exprApplyTime(date, time, false);
   }
 
   /**
diff --git a/core/src/test/java/org/opensearch/sql/expression/datetime/DateTimeTestBase.java b/core/src/test/java/org/opensearch/sql/expression/datetime/DateTimeTestBase.java
index 38beaad1315..08004a84dc4 100644
--- a/core/src/test/java/org/opensearch/sql/expression/datetime/DateTimeTestBase.java
+++ b/core/src/test/java/org/opensearch/sql/expression/datetime/DateTimeTestBase.java
@@ -6,6 +6,7 @@
 package org.opensearch.sql.expression.datetime;
 
 import static org.opensearch.sql.data.model.ExprValueUtils.fromObjectValue;
+import static org.opensearch.sql.data.type.ExprCoreType.DOUBLE;
 
 import java.time.Instant;
 import java.time.LocalDate;
@@ -81,6 +82,17 @@ protected String fromUnixTime(Double value, String format) {
         .valueOf().stringValue();
   }
 
+  protected FunctionExpression addtime(Expression date, Expression interval) {
+    var func = functionRepository.resolve(new FunctionSignature(new FunctionName("addtime"),
+        List.of(date.type(), interval.type())));
+    return (FunctionExpression)func.apply(List.of(date, interval));
+  }
+
+  protected ExprValue addtime(Temporal first, Temporal second) {
+    return addtime(DSL.literal(fromObjectValue(first)), DSL.literal(fromObjectValue(second)))
+        .valueOf(null);
+  }
+
   protected FunctionExpression maketime(Expression hour, Expression minute, Expression second) {
     return (FunctionExpression)
         functionRepository.compile(
@@ -167,8 +179,18 @@ protected Double unixTimeStampOf(LocalDateTime value) {
         .valueOf().doubleValue();
   }
 
-  protected Double unixTimeStampOf(Instant value) {
-    return unixTimeStampOf(DSL.literal(new ExprTimestampValue(value)))
-        .valueOf().doubleValue();
+  protected FunctionExpression subtime(Expression date, Expression interval) {
+    var func = functionRepository.resolve(new FunctionSignature(new FunctionName("subtime"),
+        List.of(date.type(), interval.type())));
+    return (FunctionExpression)func.apply(List.of(date, interval));
+  }
+
+  protected ExprValue subtime(Temporal first, Temporal second) {
+    return subtime(DSL.literal(fromObjectValue(first)), DSL.literal(fromObjectValue(second)))
+        .valueOf(null);
+  }
+
+  protected ExprValue eval(Expression expression) {
+    return expression.valueOf(env);
   }
 }
diff --git a/docs/user/dql/functions.rst b/docs/user/dql/functions.rst
index f7383d862d5..d9f8df0c23c 100644
--- a/docs/user/dql/functions.rst
+++ b/docs/user/dql/functions.rst
@@ -893,45 +893,13 @@ Antonyms: `SUBTIME`_
 
 Example::
 
-    os> SELECT ADDTIME(DATE('2008-12-12'), DATE('2008-11-15')) AS `'2008-12-12' + 0 `
+    os> SELECT ADDTIME(DATE('2008-12-12'), DATE('2008-11-15')) AS `'2008-12-12' + 0`, ADDTIME(TIME('23:59:59'), DATE('2004-01-01')) AS `'23:59:59' + 0`, ADDTIME(DATE('2004-01-01'), TIME('23:59:59')) AS `'2004-01-01' + '23:59:59'`, ADDTIME(TIME('10:20:30'), TIME('00:05:42')) AS `'10:20:30' + '00:05:42'`
     fetched rows / total rows = 1/1
-    +---------------------+
-    | '2008-12-12' + 0    |
-    |---------------------|
-    | 2008-12-12 00:00:00 |
-    +---------------------+
-
-    os> SELECT ADDTIME(TIME('23:59:59'), DATE('2004-01-01')) AS `'23:59:59' + 0`
-    fetched rows / total rows = 1/1
-    +------------------+
-    | '23:59:59' + 0   |
-    |------------------|
-    | 23:59:59         |
-    +------------------+
-
-    os> SELECT ADDTIME(DATE('2004-01-01'), TIME('23:59:59')) AS `'2004-01-01' + '23:59:59'`
-    fetched rows / total rows = 1/1
-    +-----------------------------+
-    | '2004-01-01' + '23:59:59'   |
-    |-----------------------------|
-    | 2004-01-01 23:59:59         |
-    +-----------------------------+
-
-    os> SELECT ADDTIME(TIME('10:20:30'), TIME('00:05:42')) AS `'10:20:30' + '00:05:42'`
-    fetched rows / total rows = 1/1
-    +---------------------------+
-    | '10:20:30' + '00:05:42'   |
-    |---------------------------|
-    | 10:26:12                  |
-    +---------------------------+
-
-    os> SELECT ADDTIME(TIMESTAMP('2007-02-28 10:20:30'), DATETIME('2002-03-04 20:40:50')) AS `'2007-02-28 10:20:30' + '20:40:50'`
-    fetched rows / total rows = 1/1
-    +--------------------------------------+
-    | '2007-02-28 10:20:30' + '20:40:50'   |
-    |--------------------------------------|
-    | 2007-03-01 07:01:20                  |
-    +--------------------------------------+
+    +---------------------+------------------+-----------------------------+---------------------------+
+    | '2008-12-12' + 0    | '23:59:59' + 0   | '2004-01-01' + '23:59:59'   | '10:20:30' + '00:05:42'   |
+    |---------------------+------------------+-----------------------------+---------------------------|
+    | 2008-12-12 00:00:00 | 23:59:59         | 2004-01-01 23:59:59         | 10:26:12                  |
+    +---------------------+------------------+-----------------------------+---------------------------+
 
 
 CONVERT_TZ
@@ -2039,80 +2007,19 @@ Argument type: DATE/DATETIME/TIMESTAMP/TIME, DATE/DATETIME/TIMESTAMP/TIME
 
 Return type map:
 
-(DATE/DATETIME/TIMESTAMP, DATE/DATETIME/TIMESTAMP/TIME) -> DATETIME
-
-(TIME, DATE/DATETIME/TIMESTAMP/TIME) -> TIME
-
-Antonyms: `ADDTIME`_
-
-Example::
-
-    os> SELECT SUBTIME(DATE('2008-12-12'), DATE('2008-11-15')) AS `'2008-12-12' - 0`
-    fetched rows / total rows = 1/1
-    +---------------------+
-    | '2008-12-12' - 0    |
-    |---------------------|
-    | 2008-12-12 00:00:00 |
-    +---------------------+
-
-    os> SELECT SUBTIME(TIME('23:59:59'), DATE('2004-01-01')) AS `'23:59:59' - 0`
-    fetched rows / total rows = 1/1
-    +------------------+
-    | '23:59:59' - 0   |
-    |------------------|
-    | 23:59:59         |
-    +------------------+
-
-    os> SELECT SUBTIME(DATE('2004-01-01'), TIME('23:59:59')) AS `'2004-01-01' - '23:59:59'`
-    fetched rows / total rows = 1/1
-    +-----------------------------+
-    | '2004-01-01' - '23:59:59'   |
-    |-----------------------------|
-    | 2003-12-31 00:00:01         |
-    +-----------------------------+
-
-    os> SELECT SUBTIME(TIME('10:20:30'), TIME('00:05:42')) AS `'10:20:30' - '00:05:42'`
-    fetched rows / total rows = 1/1
-    +---------------------------+
-    | '10:20:30' - '00:05:42'   |
-    |---------------------------|
-    | 10:14:48                  |
-    +---------------------------+
-
-    os> SELECT SUBTIME(TIMESTAMP('2007-03-01 10:20:30'), DATETIME('2002-03-04 20:40:50')) AS `'2007-03-01 10:20:30' - '20:40:50'`
-    fetched rows / total rows = 1/1
-    +--------------------------------------+
-    | '2007-03-01 10:20:30' - '20:40:50'   |
-    |--------------------------------------|
-    | 2007-02-28 13:39:40                  |
-    +--------------------------------------+
-
-
-SYSDATE
--------
-
-Description
->>>>>>>>>>>
-
-Returns the current date and time as a value in 'YYYY-MM-DD hh:mm:ss[.nnnnnn]'.
-SYSDATE() returns the time at which it executes. This differs from the behavior for `NOW() <#now>`_, which returns a constant time that indicates the time at which the statement began to execute.
-If the argument is given, it specifies a fractional seconds precision from 0 to 6, the return value includes a fractional seconds part of that many digits.
-
-Optional argument type: INTEGER
-
-Return type: DATETIME
+DATE/DATETIME/TIMESTAMP, DATE/DATETIME/TIMESTAMP/TIME -> DATETIME
 
-Specification: SYSDATE([INTEGER]) -> DATETIME
+TIME, DATE/DATETIME/TIMESTAMP/TIME -> TIME
 
 Example::
 
-    > SELECT SYSDATE() as value_1, SYSDATE(6) as value_2;
+    os> SELECT SUBTIME(DATE('2008-12-12'), DATE('2008-11-15')) AS `'2008-12-12' - 0`, SUBTIME(TIME('23:59:59'), DATE('2004-01-01')) AS `'23:59:59' - 0`, SUBTIME(DATE('2004-01-01'), TIME('23:59:59')) AS `'2004-01-01' - '23:59:59'`, SUBTIME(TIME('10:20:30'), TIME('00:05:42')) AS `'10:20:30' - '00:05:42'`
     fetched rows / total rows = 1/1
-    +---------------------+----------------------------+
-    | value_1             | value_2                    |
-    |---------------------+----------------------------|
-    | 2022-08-02 15:39:05 | 2022-08-02 15:39:05.123456 |
-    +---------------------+----------------------------+
+    +---------------------+------------------+-----------------------------+---------------------------+
+    | '2008-12-12' - 0    | '23:59:59' - 0   | '2004-01-01' - '23:59:59'   | '10:20:30' - '00:05:42'   |
+    |---------------------+------------------+-----------------------------+---------------------------|
+    | 2008-12-12 00:00:00 | 23:59:59         | 2003-12-31 00:00:01         | 10:14:48                  |
+    +---------------------+------------------+-----------------------------+---------------------------+
 
 
 TIME
diff --git a/docs/user/ppl/functions/datetime.rst b/docs/user/ppl/functions/datetime.rst
index 2cc83eba971..e713174a2ce 100644
--- a/docs/user/ppl/functions/datetime.rst
+++ b/docs/user/ppl/functions/datetime.rst
@@ -59,45 +59,13 @@ Antonyms: `SUBTIME`_
 
 Example::
 
-    os> source=people | eval `'2008-12-12' + 0` = ADDTIME(DATE('2008-12-12'), DATE('2008-11-15')) | fields `'2008-12-12' + 0`
+    os> source=people | eval `'2008-12-12' + 0` = ADDTIME(DATE('2008-12-12'), DATE('2008-11-15')), `'23:59:59' + 0` = ADDTIME(TIME('23:59:59'), DATE('2004-01-01')), `'2004-01-01' + '23:59:59'` = ADDTIME(DATE('2004-01-01'), TIME('23:59:59')), `'10:20:30' + '00:05:42'` = ADDTIME(TIME('10:20:30'), TIME('00:05:42')) | fields `'2008-12-12' + 0`, `'23:59:59' + 0`, `'2004-01-01' + '23:59:59'`, `'10:20:30' + '00:05:42'`
     fetched rows / total rows = 1/1
-    +---------------------+
-    | '2008-12-12' + 0    |
-    |---------------------|
-    | 2008-12-12 00:00:00 |
-    +---------------------+
-
-    os> source=people | eval `'23:59:59' + 0` = ADDTIME(TIME('23:59:59'), DATE('2004-01-01')) | fields `'23:59:59' + 0`
-    fetched rows / total rows = 1/1
-    +------------------+
-    | '23:59:59' + 0   |
-    |------------------|
-    | 23:59:59         |
-    +------------------+
-
-    os> source=people | eval `'2004-01-01' + '23:59:59'` = ADDTIME(DATE('2004-01-01'), TIME('23:59:59')) | fields `'2004-01-01' + '23:59:59'`
-    fetched rows / total rows = 1/1
-    +-----------------------------+
-    | '2004-01-01' + '23:59:59'   |
-    |-----------------------------|
-    | 2004-01-01 23:59:59         |
-    +-----------------------------+
-
-    os> source=people | eval `'10:20:30' + '00:05:42'` = ADDTIME(TIME('10:20:30'), TIME('00:05:42')) | fields `'10:20:30' + '00:05:42'`
-    fetched rows / total rows = 1/1
-    +---------------------------+
-    | '10:20:30' + '00:05:42'   |
-    |---------------------------|
-    | 10:26:12                  |
-    +---------------------------+
-
-    os> source=people | eval `'2007-02-28 10:20:30' + '20:40:50'` = ADDTIME(TIMESTAMP('2007-02-28 10:20:30'), DATETIME('2002-03-04 20:40:50')) | fields `'2007-02-28 10:20:30' + '20:40:50'`
-    fetched rows / total rows = 1/1
-    +--------------------------------------+
-    | '2007-02-28 10:20:30' + '20:40:50'   |
-    |--------------------------------------|
-    | 2007-03-01 07:01:20                  |
-    +--------------------------------------+
+    +---------------------+------------------+-----------------------------+---------------------------+
+    | '2008-12-12' + 0    | '23:59:59' + 0   | '2004-01-01' + '23:59:59'   | '10:20:30' + '00:05:42'   |
+    |---------------------+------------------+-----------------------------+---------------------------|
+    | 2008-12-12 00:00:00 | 23:59:59         | 2004-01-01 23:59:59         | 10:26:12                  |
+    +---------------------+------------------+-----------------------------+---------------------------+
 
 
 CONVERT_TZ
@@ -1164,72 +1132,13 @@ Antonyms: `ADDTIME`_
 
 Example::
 
-    os> source=people | eval `'2008-12-12' - 0` = SUBTIME(DATE('2008-12-12'), DATE('2008-11-15')) | fields `'2008-12-12' - 0`
-    fetched rows / total rows = 1/1
-    +---------------------+
-    | '2008-12-12' - 0    |
-    |---------------------|
-    | 2008-12-12 00:00:00 |
-    +---------------------+
-
-    os> source=people | eval `'23:59:59' - 0` = SUBTIME(TIME('23:59:59'), DATE('2004-01-01')) | fields `'23:59:59' - 0`
-    fetched rows / total rows = 1/1
-    +------------------+
-    | '23:59:59' - 0   |
-    |------------------|
-    | 23:59:59         |
-    +------------------+
-
-    os> source=people | eval `'2004-01-01' - '23:59:59'` = SUBTIME(DATE('2004-01-01'), TIME('23:59:59')) | fields `'2004-01-01' - '23:59:59'`
-    fetched rows / total rows = 1/1
-    +-----------------------------+
-    | '2004-01-01' - '23:59:59'   |
-    |-----------------------------|
-    | 2003-12-31 00:00:01         |
-    +-----------------------------+
-
-    os> source=people | eval `'10:20:30' - '00:05:42'` = SUBTIME(TIME('10:20:30'), TIME('00:05:42')) | fields `'10:20:30' - '00:05:42'`
-    fetched rows / total rows = 1/1
-    +---------------------------+
-    | '10:20:30' - '00:05:42'   |
-    |---------------------------|
-    | 10:14:48                  |
-    +---------------------------+
-
-    os> source=people | eval `'2007-03-01 10:20:30' - '20:40:50'` = SUBTIME(TIMESTAMP('2007-03-01 10:20:30'), DATETIME('2002-03-04 20:40:50')) | fields `'2007-03-01 10:20:30' - '20:40:50'`
-    fetched rows / total rows = 1/1
-    +--------------------------------------+
-    | '2007-03-01 10:20:30' - '20:40:50'   |
-    |--------------------------------------|
-    | 2007-02-28 13:39:40                  |
-    +--------------------------------------+
-
-
-SYSDATE
--------
-
-Description
->>>>>>>>>>>
-
-Returns the current date and time as a value in 'YYYY-MM-DD hh:mm:ss[.nnnnnn]'.
-SYSDATE() returns the time at which it executes. This differs from the behavior for `NOW() <#now>`_, which returns a constant time that indicates the time at which the statement began to execute.
-If the argument is given, it specifies a fractional seconds precision from 0 to 6, the return value includes a fractional seconds part of that many digits.
-
-Optional argument type: INTEGER
-
-Return type: DATETIME
-
-Specification: SYSDATE([INTEGER]) -> DATETIME
-
-Example::
-
-    > source=people | eval `value_1` = SYSDATE(), `value_2` = SYSDATE(6) | fields `value_1`, `value_2`
+    os> source=people | eval `'2008-12-12' - 0` = SUBTIME(DATE('2008-12-12'), DATE('2008-11-15')), `'23:59:59' - 0` = SUBTIME(TIME('23:59:59'), DATE('2004-01-01')), `'2004-01-01' - '23:59:59'` = SUBTIME(DATE('2004-01-01'), TIME('23:59:59')), `'10:20:30' - '00:05:42'` = SUBTIME(TIME('10:20:30'), TIME('00:05:42')) | fields `'2008-12-12' - 0`, `'23:59:59' - 0`, `'2004-01-01' - '23:59:59'`, `'10:20:30' - '00:05:42'`
     fetched rows / total rows = 1/1
-    +---------------------+----------------------------+
-    | value_1             | value_2                    |
-    |---------------------+----------------------------|
-    | 2022-08-02 15:39:05 | 2022-08-02 15:39:05.123456 |
-    +---------------------+----------------------------+
+    +---------------------+------------------+-----------------------------+---------------------------+
+    | '2008-12-12' - 0    | '23:59:59' - 0   | '2004-01-01' - '23:59:59'   | '10:20:30' - '00:05:42'   |
+    |---------------------+------------------+-----------------------------+---------------------------|
+    | 2008-12-12 00:00:00 | 23:59:59         | 2003-12-31 00:00:01         | 10:14:48                  |
+    +---------------------+------------------+-----------------------------+---------------------------+
 
 
 TIME
diff --git a/integ-test/src/test/java/org/opensearch/sql/sql/DateTimeFunctionIT.java b/integ-test/src/test/java/org/opensearch/sql/sql/DateTimeFunctionIT.java
index f10596e21c3..fd87a6d4e3f 100644
--- a/integ-test/src/test/java/org/opensearch/sql/sql/DateTimeFunctionIT.java
+++ b/integ-test/src/test/java/org/opensearch/sql/sql/DateTimeFunctionIT.java
@@ -826,25 +826,6 @@ public void testUnixTimeStamp() throws IOException {
   }
 
   @Test
-  public void testPeriodAdd() throws IOException {
-    var result = executeQuery(
-        "select PERIOD_ADD(200801, 2) as f1, PERIOD_ADD(200801, -12) as f2");
-    verifySchema(result,
-        schema("PERIOD_ADD(200801, 2)", "f1", "integer"),
-        schema("PERIOD_ADD(200801, -12)", "f2", "integer"));
-    verifyDataRows(result, rows(200803, 200701));
-  }
-
-  @Test
-  public void testPeriodDiff() throws IOException {
-    var result = executeQuery(
-        "select PERIOD_DIFF(200802, 200703) as f1, PERIOD_DIFF(200802, 201003) as f2");
-    verifySchema(result,
-        schema("PERIOD_DIFF(200802, 200703)", "f1", "integer"),
-        schema("PERIOD_DIFF(200802, 201003)", "f2", "integer"));
-    verifyDataRows(result, rows(11, -25));
-  }
-
   public void testAddTime() throws IOException {
     var result = executeQuery("SELECT"
         + " ADDTIME(DATE('2008-12-12'), DATE('2008-11-15')) AS `'2008-12-12' + 0`,"
diff --git a/ppl/src/main/antlr/OpenSearchPPLParser.g4 b/ppl/src/main/antlr/OpenSearchPPLParser.g4
index 9cb539cfbaa..edc33983a4a 100644
--- a/ppl/src/main/antlr/OpenSearchPPLParser.g4
+++ b/ppl/src/main/antlr/OpenSearchPPLParser.g4
@@ -428,53 +428,17 @@ trigonometricFunctionName
     ;
 
 dateAndTimeFunctionBase
-    : ADDDATE
-    | ADDTIME
-    | CONVERT_TZ
-    | CURRENT_DATE
-    | CURRENT_TIME
-    | CURRENT_TIMESTAMP
-    | DATE
-    | DATE_ADD
-    | DATE_FORMAT
-    | DATE_SUB
-    | DATETIME
-    | DAY
-    | DAYNAME
-    | DAYOFMONTH
-    | DAYOFWEEK
-    | DAYOFYEAR
-    | CURDATE
-    | CURTIME
-    | FROM_DAYS
-    | FROM_UNIXTIME
-    | HOUR
-    | LOCALTIME
-    | LOCALTIMESTAMP
-    | MAKEDATE
-    | MAKETIME
-    | MICROSECOND
-    | MINUTE
-    | MONTH
-    | MONTHNAME
-    | NOW
-    | PERIOD_ADD
-    | PERIOD_DIFF
-    | QUARTER
-    | SECOND
-    | SUBDATE
-    | SUBTIME
-    | SYSDATE
-    | TIME
-    | TIME_TO_SEC
-    | TIMESTAMP
-    | TO_DAYS
-    | UNIX_TIMESTAMP
-    | UTC_DATE
-    | UTC_TIME
-    | UTC_TIMESTAMP
-    | WEEK
-    | YEAR
+    : ADDDATE | ADDTIME | CONVERT_TZ | DATE | DATE_ADD | DATE_FORMAT | DATE_SUB
+    | DATETIME | DAY | DAYNAME | DAYOFMONTH | DAYOFWEEK | DAYOFYEAR | FROM_DAYS | FROM_UNIXTIME
+    | HOUR | MAKEDATE | MAKETIME | MICROSECOND | MINUTE | MONTH | MONTHNAME
+    | QUARTER | SECOND | SUBDATE | SUBTIME | SYSDATE | TIME | TIME_TO_SEC
+    | TIMESTAMP | TO_DAYS | UNIX_TIMESTAMP | WEEK | YEAR
+    ;
+
+// Functions which value could be cached in scope of a single query
+constantFunctionName
+    : datetimeConstantLiteral
+    | CURDATE | CURTIME | NOW
     ;
 
 /** condition function return boolean value */
diff --git a/sql/src/main/antlr/OpenSearchSQLParser.g4 b/sql/src/main/antlr/OpenSearchSQLParser.g4
index 1598e7676cb..3076727b55e 100644
--- a/sql/src/main/antlr/OpenSearchSQLParser.g4
+++ b/sql/src/main/antlr/OpenSearchSQLParser.g4
@@ -411,6 +411,15 @@ trigonometricFunctionName
     ;
 
 dateTimeFunctionName
+    : ADDDATE | ADDTIME | CONVERT_TZ | DATE | DATE_ADD | DATE_FORMAT | DATE_SUB
+    | DATETIME | DAY | DAYNAME | DAYOFMONTH | DAYOFWEEK | DAYOFYEAR | FROM_DAYS | FROM_UNIXTIME
+    | HOUR | MAKEDATE | MAKETIME | MICROSECOND | MINUTE | MONTH | MONTHNAME
+    | QUARTER | SECOND | SUBDATE | SUBTIME | SYSDATE | TIME | TIME_TO_SEC
+    | TIMESTAMP | TO_DAYS | UNIX_TIMESTAMP | WEEK | YEAR
+    ;
+
+// Functions which value could be cached in scope of a single query
+constantFunctionName
     : datetimeConstantLiteral
     | ADDDATE
     | ADDTIME

From 3b01e6b202a8e0b9bee56f260c1c19b06d901810 Mon Sep 17 00:00:00 2001
From: Yury-Fridlyand <yuryf@bitquilltech.com>
Date: Tue, 11 Oct 2022 20:25:40 -0700
Subject: [PATCH 02/14] Update docs - rework on examples.

Signed-off-by: Yury-Fridlyand <yuryf@bitquilltech.com>
---
 docs/user/dql/functions.rst          | 93 +++++++++++++++++++++++-----
 docs/user/ppl/functions/datetime.rst | 88 ++++++++++++++++++++++----
 2 files changed, 155 insertions(+), 26 deletions(-)

diff --git a/docs/user/dql/functions.rst b/docs/user/dql/functions.rst
index d9f8df0c23c..3e363efb820 100644
--- a/docs/user/dql/functions.rst
+++ b/docs/user/dql/functions.rst
@@ -893,13 +893,45 @@ Antonyms: `SUBTIME`_
 
 Example::
 
-    os> SELECT ADDTIME(DATE('2008-12-12'), DATE('2008-11-15')) AS `'2008-12-12' + 0`, ADDTIME(TIME('23:59:59'), DATE('2004-01-01')) AS `'23:59:59' + 0`, ADDTIME(DATE('2004-01-01'), TIME('23:59:59')) AS `'2004-01-01' + '23:59:59'`, ADDTIME(TIME('10:20:30'), TIME('00:05:42')) AS `'10:20:30' + '00:05:42'`
+    os> SELECT ADDTIME(TIME('23:59:59'), DATE('2004-01-01')) AS `'23:59:59' + 0`
     fetched rows / total rows = 1/1
-    +---------------------+------------------+-----------------------------+---------------------------+
-    | '2008-12-12' + 0    | '23:59:59' + 0   | '2004-01-01' + '23:59:59'   | '10:20:30' + '00:05:42'   |
-    |---------------------+------------------+-----------------------------+---------------------------|
-    | 2008-12-12 00:00:00 | 23:59:59         | 2004-01-01 23:59:59         | 10:26:12                  |
-    +---------------------+------------------+-----------------------------+---------------------------+
+    +---------------------+
+    | '2008-12-12' + 0    |
+    |---------------------|
+    | 2008-12-12 00:00:00 |
+    +---------------------+
+
+    os> SELECT ADDTIME(TIME('23:59:59'), DATE('2004-01-01')) AS `'23:59:59' + 0`
+    fetched rows / total rows = 1/1
+    +------------------+
+    | '23:59:59' + 0   |
+    |------------------|
+    | 23:59:59         |
+    +------------------+
+
+    os> SELECT ADDTIME(DATE('2004-01-01'), TIME('23:59:59')) AS `'2004-01-01' + '23:59:59'`
+    fetched rows / total rows = 1/1
+    +-----------------------------+
+    | '2004-01-01' + '23:59:59'   |
+    |-----------------------------|
+    | 2004-01-01 23:59:59         |
+    +-----------------------------+
+
+    os> SELECT ADDTIME(TIME('10:20:30'), TIME('00:05:42')) AS `'10:20:30' + '00:05:42'`
+    fetched rows / total rows = 1/1
+    +---------------------------+
+    | '10:20:30' + '00:05:42'   |
+    |---------------------------|
+    | 10:26:12                  |
+    +---------------------------+
+
+    os> SELECT ADDTIME(TIMESTAMP('2007-02-28 10:20:30'), DATETIME('2002-03-04 20:40:50')) AS `'2007-02-28 10:20:30' + '20:40:50'`
+    fetched rows / total rows = 1/1
+    +--------------------------------------+
+    | '2007-02-28 10:20:30' + '20:40:50'   |
+    |--------------------------------------|
+    | 2007-03-01 07:01:20                  |
+    +--------------------------------------+
 
 
 CONVERT_TZ
@@ -2007,20 +2039,53 @@ Argument type: DATE/DATETIME/TIMESTAMP/TIME, DATE/DATETIME/TIMESTAMP/TIME
 
 Return type map:
 
-DATE/DATETIME/TIMESTAMP, DATE/DATETIME/TIMESTAMP/TIME -> DATETIME
+(DATE/DATETIME/TIMESTAMP, DATE/DATETIME/TIMESTAMP/TIME) -> DATETIME
+
+(TIME, DATE/DATETIME/TIMESTAMP/TIME) -> TIME
 
-TIME, DATE/DATETIME/TIMESTAMP/TIME -> TIME
+Antonyms: `ADDTIME`_
 
 Example::
 
-    os> SELECT SUBTIME(DATE('2008-12-12'), DATE('2008-11-15')) AS `'2008-12-12' - 0`, SUBTIME(TIME('23:59:59'), DATE('2004-01-01')) AS `'23:59:59' - 0`, SUBTIME(DATE('2004-01-01'), TIME('23:59:59')) AS `'2004-01-01' - '23:59:59'`, SUBTIME(TIME('10:20:30'), TIME('00:05:42')) AS `'10:20:30' - '00:05:42'`
+    os> SELECT SUBTIME(DATE('2008-12-12'), DATE('2008-11-15')) AS `'2008-12-12' - 0`
     fetched rows / total rows = 1/1
-    +---------------------+------------------+-----------------------------+---------------------------+
-    | '2008-12-12' - 0    | '23:59:59' - 0   | '2004-01-01' - '23:59:59'   | '10:20:30' - '00:05:42'   |
-    |---------------------+------------------+-----------------------------+---------------------------|
-    | 2008-12-12 00:00:00 | 23:59:59         | 2003-12-31 00:00:01         | 10:14:48                  |
-    +---------------------+------------------+-----------------------------+---------------------------+
+    +---------------------+
+    | '2008-12-12' - 0    |
+    |---------------------|
+    | 2008-12-12 00:00:00 |
+    +---------------------+
+
+    os> SELECT SUBTIME(TIME('23:59:59'), DATE('2004-01-01')) AS `'23:59:59' - 0`
+    fetched rows / total rows = 1/1
+    +------------------+
+    | '23:59:59' - 0   |
+    |------------------|
+    | 23:59:59         |
+    +------------------+
+
+    os> SELECT SUBTIME(DATE('2004-01-01'), TIME('23:59:59')) AS `'2004-01-01' - '23:59:59'`
+    fetched rows / total rows = 1/1
+    +-----------------------------+
+    | '2004-01-01' - '23:59:59'   |
+    |-----------------------------|
+    | 2003-12-31 00:00:01         |
+    +-----------------------------+
 
+    os> SELECT SUBTIME(TIME('10:20:30'), TIME('00:05:42')) AS `'10:20:30' - '00:05:42'`
+    fetched rows / total rows = 1/1
+    +---------------------------+
+    | '10:20:30' - '00:05:42'   |
+    |---------------------------|
+    | 10:14:48                  |
+    +---------------------------+
+
+    os> SELECT SUBTIME(TIMESTAMP('2007-03-01 10:20:30'), DATETIME('2002-03-04 20:40:50')) AS `'2007-03-01 10:20:30' - '20:40:50'`
+    fetched rows / total rows = 1/1
+    +-----------------------------------------+
+    | `'2007-03-01 10:20:30' - '20:40:50'`    |
+    |-----------------------------------------|
+    | 2007-02-28 13:39:40                     |
+    +-----------------------------------------+
 
 TIME
 ----
diff --git a/docs/user/ppl/functions/datetime.rst b/docs/user/ppl/functions/datetime.rst
index e713174a2ce..ae893a5e8b0 100644
--- a/docs/user/ppl/functions/datetime.rst
+++ b/docs/user/ppl/functions/datetime.rst
@@ -59,13 +59,45 @@ Antonyms: `SUBTIME`_
 
 Example::
 
-    os> source=people | eval `'2008-12-12' + 0` = ADDTIME(DATE('2008-12-12'), DATE('2008-11-15')), `'23:59:59' + 0` = ADDTIME(TIME('23:59:59'), DATE('2004-01-01')), `'2004-01-01' + '23:59:59'` = ADDTIME(DATE('2004-01-01'), TIME('23:59:59')), `'10:20:30' + '00:05:42'` = ADDTIME(TIME('10:20:30'), TIME('00:05:42')) | fields `'2008-12-12' + 0`, `'23:59:59' + 0`, `'2004-01-01' + '23:59:59'`, `'10:20:30' + '00:05:42'`
+    os> source=people | eval `'2008-12-12' + 0` = ADDTIME(DATE('2008-12-12'), DATE('2008-11-15')) | fields `'2008-12-12' + 0`
     fetched rows / total rows = 1/1
-    +---------------------+------------------+-----------------------------+---------------------------+
-    | '2008-12-12' + 0    | '23:59:59' + 0   | '2004-01-01' + '23:59:59'   | '10:20:30' + '00:05:42'   |
-    |---------------------+------------------+-----------------------------+---------------------------|
-    | 2008-12-12 00:00:00 | 23:59:59         | 2004-01-01 23:59:59         | 10:26:12                  |
-    +---------------------+------------------+-----------------------------+---------------------------+
+    +---------------------+
+    | '2008-12-12' + 0    |
+    |---------------------|
+    | 2008-12-12 00:00:00 |
+    +---------------------+
+
+    os> source=people | `'23:59:59' + 0` = ADDTIME(TIME('23:59:59'), DATE('2004-01-01')) | fields `'23:59:59' + 0`
+    fetched rows / total rows = 1/1
+    +------------------+
+    | '23:59:59' + 0   |
+    |------------------|
+    | 23:59:59         |
+    +------------------+
+
+    os> source=people | eval `'2004-01-01' + '23:59:59'` = ADDTIME(DATE('2004-01-01'), TIME('23:59:59')) | fields `'2004-01-01' + '23:59:59'`
+    fetched rows / total rows = 1/1
+    +-----------------------------+
+    | '2004-01-01' + '23:59:59'   |
+    |-----------------------------|
+    | 2004-01-01 23:59:59         |
+    +-----------------------------+
+
+    os> source=people | eval `'10:20:30' + '00:05:42'` = ADDTIME(TIME('10:20:30'), TIME('00:05:42')) | fields `'10:20:30' + '00:05:42'`
+    fetched rows / total rows = 1/1
+    +---------------------------+
+    | '10:20:30' + '00:05:42'   |
+    |---------------------------|
+    | 10:26:12                  |
+    +---------------------------+
+
+    os> source=people | eval `'2007-02-28 10:20:30' + '20:40:50'` = ADDTIME(TIMESTAMP('2007-02-28 10:20:30'), DATETIME('2002-03-04 20:40:50')) | fields `'2007-02-28 10:20:30' + '20:40:50'`
+    fetched rows / total rows = 1/1
+    +--------------------------------------+
+    | '2007-02-28 10:20:30' + '20:40:50'   |
+    |--------------------------------------|
+    | 2007-03-01 07:01:20                  |
+    +--------------------------------------+
 
 
 CONVERT_TZ
@@ -1132,13 +1164,45 @@ Antonyms: `ADDTIME`_
 
 Example::
 
-    os> source=people | eval `'2008-12-12' - 0` = SUBTIME(DATE('2008-12-12'), DATE('2008-11-15')), `'23:59:59' - 0` = SUBTIME(TIME('23:59:59'), DATE('2004-01-01')), `'2004-01-01' - '23:59:59'` = SUBTIME(DATE('2004-01-01'), TIME('23:59:59')), `'10:20:30' - '00:05:42'` = SUBTIME(TIME('10:20:30'), TIME('00:05:42')) | fields `'2008-12-12' - 0`, `'23:59:59' - 0`, `'2004-01-01' - '23:59:59'`, `'10:20:30' - '00:05:42'`
+    os> source=people | eval `'2008-12-12' - 0` = SUBTIME(DATE('2008-12-12'), DATE('2008-11-15')) | fields `'2008-12-12' - 0`
+    fetched rows / total rows = 1/1
+    +---------------------+
+    | '2008-12-12' - 0    |
+    |---------------------|
+    | 2008-12-12 00:00:00 |
+    +---------------------+
+
+    os> source=people | eval `'23:59:59' - 0` = SUBTIME(TIME('23:59:59'), DATE('2004-01-01')) | fields `'23:59:59' - 0`
+    fetched rows / total rows = 1/1
+    +------------------+
+    | '23:59:59' - 0   |
+    |------------------|
+    | 23:59:59         |
+    +------------------+
+
+    os> source=people | eval `'2004-01-01' - '23:59:59'` = SUBTIME(DATE('2004-01-01'), TIME('23:59:59')) | fields `'2004-01-01' - '23:59:59'`
+    fetched rows / total rows = 1/1
+    +-----------------------------+
+    | '2004-01-01' - '23:59:59'   |
+    |-----------------------------|
+    | 2003-12-31 00:00:01         |
+    +-----------------------------+
+
+    os> source=people | eval `'10:20:30' - '00:05:42'` = SUBTIME(TIME('10:20:30'), TIME('00:05:42')) | fields `'10:20:30' - '00:05:42'`
+    fetched rows / total rows = 1/1
+    +---------------------------+
+    | '10:20:30' - '00:05:42'   |
+    |---------------------------|
+    | 10:14:48                  |
+    +---------------------------+
+
+    os> source=people | eval `'2007-03-01 10:20:30' - '20:40:50'` = SUBTIME(TIMESTAMP('2007-03-01 10:20:30'), DATETIME('2002-03-04 20:40:50')) | fields `'2007-03-01 10:20:30' - '20:40:50'`
     fetched rows / total rows = 1/1
-    +---------------------+------------------+-----------------------------+---------------------------+
-    | '2008-12-12' - 0    | '23:59:59' - 0   | '2004-01-01' - '23:59:59'   | '10:20:30' - '00:05:42'   |
-    |---------------------+------------------+-----------------------------+---------------------------|
-    | 2008-12-12 00:00:00 | 23:59:59         | 2003-12-31 00:00:01         | 10:14:48                  |
-    +---------------------+------------------+-----------------------------+---------------------------+
+    +-----------------------------------------+
+    | `'2007-03-01 10:20:30' - '20:40:50'`    |
+    |-----------------------------------------|
+    | 2007-02-28 13:39:40                     |
+    +-----------------------------------------+
 
 
 TIME

From fbabe78ad5ac65981c0ec241465479f1f58848b8 Mon Sep 17 00:00:00 2001
From: Yury-Fridlyand <yuryf@bitquilltech.com>
Date: Wed, 12 Oct 2022 19:16:32 -0700
Subject: [PATCH 03/14] Update `ExprTimeValue` by `datetimeValue` and other
 interfaces. Add corresponding tests.

Signed-off-by: Yury-Fridlyand <yuryf@bitquilltech.com>
---
 .../sql/data/model/ExprTimeValue.java         | 17 +++++++++++++++
 .../sql/data/model/DateTimeValueTest.java     | 21 ++++---------------
 2 files changed, 21 insertions(+), 17 deletions(-)

diff --git a/core/src/main/java/org/opensearch/sql/data/model/ExprTimeValue.java b/core/src/main/java/org/opensearch/sql/data/model/ExprTimeValue.java
index d77a2615d26..a1019acdbbb 100644
--- a/core/src/main/java/org/opensearch/sql/data/model/ExprTimeValue.java
+++ b/core/src/main/java/org/opensearch/sql/data/model/ExprTimeValue.java
@@ -13,7 +13,9 @@
 import java.time.LocalDate;
 import java.time.LocalDateTime;
 import java.time.LocalTime;
+import java.time.ZoneId;
 import java.time.ZonedDateTime;
+import java.time.format.DateTimeFormatter;
 import java.time.format.DateTimeParseException;
 import java.util.Objects;
 import lombok.RequiredArgsConstructor;
@@ -70,6 +72,21 @@ public Instant timestampValue(FunctionProperties functionProperties) {
         .toInstant();
   }
 
+  @Override
+  public LocalDate dateValue() {
+    return LocalDate.now();
+  }
+
+  @Override
+  public LocalDateTime datetimeValue() {
+    return LocalDateTime.of(dateValue(), timeValue());
+  }
+
+  @Override
+  public Instant timestampValue() {
+    return ZonedDateTime.of(dateValue(), timeValue(), ZoneId.systemDefault()).toInstant();
+  }
+
   @Override
   public String toString() {
     return String.format("TIME '%s'", value());
diff --git a/core/src/test/java/org/opensearch/sql/data/model/DateTimeValueTest.java b/core/src/test/java/org/opensearch/sql/data/model/DateTimeValueTest.java
index a335478e193..4fc4a7d563f 100644
--- a/core/src/test/java/org/opensearch/sql/data/model/DateTimeValueTest.java
+++ b/core/src/test/java/org/opensearch/sql/data/model/DateTimeValueTest.java
@@ -32,23 +32,10 @@ public void timeValueInterfaceTest() {
     assertEquals(TIME, timeValue.type());
 
     assertEquals(LocalTime.parse("01:01:01"), timeValue.timeValue());
-    // It is prohibited to acquire values which include date part from `ExprTimeValue`
-    // without a FunctionProperties object
-    var exception = assertThrows(ExpressionEvaluationException.class, timeValue::dateValue);
-    assertEquals("invalid to get dateValue from value of type TIME", exception.getMessage());
-    exception = assertThrows(ExpressionEvaluationException.class, timeValue::datetimeValue);
-    assertEquals("invalid to get datetimeValue from value of type TIME", exception.getMessage());
-    exception = assertThrows(ExpressionEvaluationException.class, timeValue::timestampValue);
-    assertEquals("invalid to get timestampValue from value of type TIME", exception.getMessage());
-
-    var functionProperties = new FunctionProperties();
-    var today = LocalDate.now(functionProperties.getQueryStartClock());
-
-    assertEquals(today, timeValue.dateValue(functionProperties));
-    assertEquals(today.atTime(1, 1, 1), timeValue.datetimeValue(functionProperties));
-    assertEquals(ZonedDateTime.of(LocalTime.parse("01:01:01").atDate(today),
-        ExprTimestampValue.ZONE).toInstant(), timeValue.timestampValue(functionProperties));
-
+    assertEquals(LocalDate.now(), timeValue.dateValue());
+    assertEquals(LocalDate.now().atTime(1, 1, 1), timeValue.datetimeValue());
+    assertEquals(ZonedDateTime.of(LocalTime.parse("01:01:01").atDate(LocalDate.now()),
+        ZoneId.systemDefault()).toInstant(), timeValue.timestampValue());
     assertEquals("01:01:01", timeValue.value());
     assertEquals("TIME '01:01:01'", timeValue.toString());
     exception = assertThrows(ExpressionEvaluationException.class,

From 533281cf367f141f4019439456d6108ffed0d3b5 Mon Sep 17 00:00:00 2001
From: Yury-Fridlyand <yuryf@bitquilltech.com>
Date: Thu, 13 Oct 2022 17:57:13 -0700
Subject: [PATCH 04/14] Update `TIMESTAMP` function implementation and
 signatures.

Signed-off-by: Yury-Fridlyand <yuryf@bitquilltech.com>
---
 .../expression/datetime/DateTimeFunction.java | 45 ++++++++++++++-----
 1 file changed, 35 insertions(+), 10 deletions(-)

diff --git a/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java b/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
index f33534801e6..cf9a9772619 100644
--- a/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
+++ b/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
@@ -598,15 +598,32 @@ private DefaultFunctionResolver time_to_sec() {
 
   /**
    * Extracts the timestamp of a date and time value.
-   * Also to construct a date type. The supported signatures:
-   * STRING/DATE/DATETIME/TIMESTAMP -> DATE
+   *
+   * DATE/TIME/DATETIME/TIMESTAMP -> TIMESTAMP
+   * DATE/TIME/DATETIME/TIMESTAMP, DATE/TIME/DATETIME/TIMESTAMP -> TIMESTAMP
    */
   private DefaultFunctionResolver timestamp() {
     return define(BuiltinFunctionName.TIMESTAMP.getName(),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestamp), TIMESTAMP, STRING),
         impl(nullMissingHandling(DateTimeFunction::exprTimestamp), TIMESTAMP, DATE),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestamp), TIMESTAMP, TIME),
         impl(nullMissingHandling(DateTimeFunction::exprTimestamp), TIMESTAMP, DATETIME),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestamp), TIMESTAMP, TIMESTAMP));
+        impl(nullMissingHandling(DateTimeFunction::exprTimestamp), TIMESTAMP, TIMESTAMP),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATE, DATE),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATE, TIME),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATE, DATETIME),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATE, TIMESTAMP),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIME, DATE),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIME, TIME),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIME, DATETIME),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIME, TIMESTAMP),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATETIME, DATE),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATETIME, TIME),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATETIME, DATETIME),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATETIME, TIMESTAMP),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIMESTAMP, DATE),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIMESTAMP, TIME),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIMESTAMP, DATETIME),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIMESTAMP, TIMESTAMP));
   }
 
   /**
@@ -1151,15 +1168,23 @@ private ExprValue exprTime(ExprValue exprValue) {
   /**
    * Timestamp implementation for ExprValue.
    *
-   * @param exprValue ExprValue of Timestamp type or String type.
+   * @param exprValue ExprValue of Timestamp.
    * @return ExprValue.
    */
   private ExprValue exprTimestamp(ExprValue exprValue) {
-    if (exprValue instanceof ExprStringValue) {
-      return new ExprTimestampValue(exprValue.stringValue());
-    } else {
-      return new ExprTimestampValue(exprValue.timestampValue());
-    }
+    return new ExprTimestampValue(exprValue.timestampValue());
+  }
+
+  /**
+   * Timestamp implementation for two arguments. It adds the time expression exprValue2
+   * to the expression exprValue2 and returns the result as a timestamp value.
+   *
+   * @param exprValue1 ExprValue of Timestamp type or String type.
+   * @param exprValue2 ExprValue of Timestamp type or String type.
+   * @return ExprValue.
+   */
+  private ExprValue exprTimestampEx(ExprValue exprValue1, ExprValue exprValue2) {
+    return exprAddTime(exprTimestamp(exprValue1), exprTimestamp(exprValue2));
   }
 
   /**

From 80affb7179d3e2aeb12fa16cb88111f7734130a9 Mon Sep 17 00:00:00 2001
From: Yury-Fridlyand <yuryf@bitquilltech.com>
Date: Fri, 14 Oct 2022 09:58:33 -0700
Subject: [PATCH 05/14] Modify function to accept strings.

Signed-off-by: Yury-Fridlyand <yuryf@bitquilltech.com>
---
 .../expression/datetime/DateTimeFunction.java | 33 +++++++++++++++----
 1 file changed, 26 insertions(+), 7 deletions(-)

diff --git a/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java b/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
index cf9a9772619..5ade73d71bc 100644
--- a/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
+++ b/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
@@ -598,32 +598,47 @@ private DefaultFunctionResolver time_to_sec() {
 
   /**
    * Extracts the timestamp of a date and time value.
+   * Input strings may contain a timestamp only in format 'yyyy-MM-dd HH:mm:ss[.SSSSSSSSS]'
    *
-   * DATE/TIME/DATETIME/TIMESTAMP -> TIMESTAMP
-   * DATE/TIME/DATETIME/TIMESTAMP, DATE/TIME/DATETIME/TIMESTAMP -> TIMESTAMP
+   * STRING/DATE/TIME/DATETIME/TIMESTAMP -> TIMESTAMP
+   * STRING/DATE/TIME/DATETIME/TIMESTAMP, STRING/DATE/TIME/DATETIME/TIMESTAMP -> TIMESTAMP
    */
   private DefaultFunctionResolver timestamp() {
     return define(BuiltinFunctionName.TIMESTAMP.getName(),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestamp), TIMESTAMP, STRING),
         impl(nullMissingHandling(DateTimeFunction::exprTimestamp), TIMESTAMP, DATE),
         impl(nullMissingHandling(DateTimeFunction::exprTimestamp), TIMESTAMP, TIME),
         impl(nullMissingHandling(DateTimeFunction::exprTimestamp), TIMESTAMP, DATETIME),
         impl(nullMissingHandling(DateTimeFunction::exprTimestamp), TIMESTAMP, TIMESTAMP),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, STRING, STRING),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, STRING, DATE),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, STRING, TIME),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, STRING, DATETIME),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, STRING, TIMESTAMP),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATE, STRING),
         impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATE, DATE),
         impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATE, TIME),
         impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATE, DATETIME),
         impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATE, TIMESTAMP),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIME, STRING),
         impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIME, DATE),
         impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIME, TIME),
         impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIME, DATETIME),
         impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIME, TIMESTAMP),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATETIME, STRING),
         impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATETIME, DATE),
         impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATETIME, TIME),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATETIME, DATETIME),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATETIME, TIMESTAMP),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, DATETIME, DATETIME),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, DATETIME, TIMESTAMP),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIMESTAMP, STRING),
         impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIMESTAMP, DATE),
         impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIMESTAMP, TIME),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIMESTAMP, DATETIME),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIMESTAMP, TIMESTAMP));
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, TIMESTAMP, DATETIME),
+        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, TIMESTAMP, TIMESTAMP));
   }
 
   /**
@@ -1172,7 +1187,11 @@ private ExprValue exprTime(ExprValue exprValue) {
    * @return ExprValue.
    */
   private ExprValue exprTimestamp(ExprValue exprValue) {
-    return new ExprTimestampValue(exprValue.timestampValue());
+    if (exprValue instanceof ExprStringValue) {
+      return new ExprTimestampValue(exprValue.stringValue());
+    } else {
+      return new ExprTimestampValue(exprValue.timestampValue());
+    }
   }
 
   /**

From e7db9700d83427fa4ad4439323ae4e3c13262daa Mon Sep 17 00:00:00 2001
From: Yury-Fridlyand <yuryf@bitquilltech.com>
Date: Sun, 16 Oct 2022 11:22:44 -0700
Subject: [PATCH 06/14] Return `NULL` on invalid string input.

Signed-off-by: Yury-Fridlyand <yuryf@bitquilltech.com>
---
 .../sql/expression/datetime/DateTimeFunction.java           | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java b/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
index 5ade73d71bc..2b25827d850 100644
--- a/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
+++ b/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
@@ -1188,7 +1188,11 @@ private ExprValue exprTime(ExprValue exprValue) {
    */
   private ExprValue exprTimestamp(ExprValue exprValue) {
     if (exprValue instanceof ExprStringValue) {
-      return new ExprTimestampValue(exprValue.stringValue());
+      try {
+        return new ExprTimestampValue(exprValue.stringValue());
+      } catch (SemanticCheckException ignored) {
+        return ExprNullValue.of();
+      }
     } else {
       return new ExprTimestampValue(exprValue.timestampValue());
     }

From df0b27c64b5060a7fb4367751a73531f9fdad33e Mon Sep 17 00:00:00 2001
From: Yury-Fridlyand <yuryf@bitquilltech.com>
Date: Thu, 20 Oct 2022 15:10:45 -0700
Subject: [PATCH 07/14] Add unit tests.

Signed-off-by: Yury-Fridlyand <yuryf@bitquilltech.com>
---
 .../expression/datetime/DateTimeFunction.java |   4 +-
 .../expression/datetime/TimestampTest.java    | 186 ++++++++++++++++++
 2 files changed, 188 insertions(+), 2 deletions(-)
 create mode 100644 core/src/test/java/org/opensearch/sql/expression/datetime/TimestampTest.java

diff --git a/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java b/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
index 2b25827d850..16c193ecbe7 100644
--- a/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
+++ b/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
@@ -1199,8 +1199,8 @@ private ExprValue exprTimestamp(ExprValue exprValue) {
   }
 
   /**
-   * Timestamp implementation for two arguments. It adds the time expression exprValue2
-   * to the expression exprValue2 and returns the result as a timestamp value.
+   * Timestamp implementation for two arguments. It extracts time expression from exprValue2
+   * and adds it to the expression exprValue1 and returns the result as a timestamp value.
    *
    * @param exprValue1 ExprValue of Timestamp type or String type.
    * @param exprValue2 ExprValue of Timestamp type or String type.
diff --git a/core/src/test/java/org/opensearch/sql/expression/datetime/TimestampTest.java b/core/src/test/java/org/opensearch/sql/expression/datetime/TimestampTest.java
new file mode 100644
index 00000000000..68e7e59897c
--- /dev/null
+++ b/core/src/test/java/org/opensearch/sql/expression/datetime/TimestampTest.java
@@ -0,0 +1,186 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.sql.expression.datetime;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.opensearch.sql.data.type.ExprCoreType.TIMESTAMP;
+
+import java.time.Instant;
+import java.time.LocalDate;
+import java.time.LocalDateTime;
+import java.time.LocalTime;
+import java.util.stream.Stream;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.opensearch.sql.data.model.ExprNullValue;
+import org.opensearch.sql.data.model.ExprTimestampValue;
+import org.opensearch.sql.data.model.ExprValue;
+import org.opensearch.sql.data.model.ExprValueUtils;
+import org.opensearch.sql.expression.DSL;
+import org.opensearch.sql.expression.Expression;
+import org.opensearch.sql.expression.ExpressionTestBase;
+import org.opensearch.sql.expression.env.Environment;
+
+@ExtendWith(MockitoExtension.class)
+public class TimestampTest extends ExpressionTestBase {
+
+  @Mock
+  Environment<Expression, ExprValue> env;
+
+  @Test
+  public void timestamp_one_arg_string() {
+    var expr = dsl.timestamp(DSL.literal("1961-04-12 09:07:00"));
+    assertEquals(TIMESTAMP, expr.type());
+    assertEquals(new ExprTimestampValue("1961-04-12 09:07:00"), expr.valueOf(env));
+
+    expr = dsl.timestamp(DSL.literal("1961-04-12 09:07:00.123456"));
+    assertEquals(TIMESTAMP, expr.type());
+    assertEquals(LocalDateTime.of(1961, 4, 12, 9, 7, 0, 123456000),
+        expr.valueOf(env).datetimeValue());
+  }
+
+  @Test
+  public void timestamp_one_arg_string_invalid_format() {
+    // Feb 30th
+    var expr = dsl.timestamp(DSL.literal("1984-02-30 12:20:42"));
+    assertEquals(TIMESTAMP, expr.type());
+    assertEquals(ExprNullValue.of(), expr.valueOf(env));
+
+    // 24:00:00
+    expr = dsl.timestamp(DSL.literal("1984-02-10 24:00:00"));
+    assertEquals(TIMESTAMP, expr.type());
+    assertEquals(ExprNullValue.of(), expr.valueOf(env));
+
+    // 2 digit year
+    expr = dsl.timestamp(DSL.literal("84-02-10 12:20:42"));
+    assertEquals(TIMESTAMP, expr.type());
+    assertEquals(ExprNullValue.of(), expr.valueOf(env));
+  }
+
+  @Test
+  public void timestamp_one_arg_time() {
+    var expr = dsl.timestamp(dsl.time(DSL.literal("22:33:44")));
+    assertEquals(TIMESTAMP, expr.type());
+    var refValue = LocalDate.now().atTime(LocalTime.of(22, 33, 44))
+        .atZone(ExprTimestampValue.ZONE).toInstant();
+    assertEquals(new ExprTimestampValue(refValue), expr.valueOf(env));
+  }
+
+  @Test
+  public void timestamp_one_arg_date() {
+    var expr = dsl.timestamp(dsl.date(DSL.literal("2077-12-15")));
+    assertEquals(TIMESTAMP, expr.type());
+    var refValue = LocalDate.of(2077, 12, 15).atStartOfDay()
+        .atZone(ExprTimestampValue.ZONE).toInstant();
+    assertEquals(new ExprTimestampValue(refValue), expr.valueOf(env));
+  }
+
+  @Test
+  public void timestamp_one_arg_datetime() {
+    var expr = dsl.timestamp(dsl.datetime(DSL.literal("1961-04-12 09:07:00")));
+    assertEquals(TIMESTAMP, expr.type());
+    assertEquals(LocalDateTime.of(1961, 4, 12, 9, 7, 0), expr.valueOf(env).datetimeValue());
+  }
+
+  @Test
+  public void timestamp_one_arg_timestamp() {
+    var refValue = new ExprTimestampValue(Instant.ofEpochSecond(10050042));
+    var expr = dsl.timestamp(dsl.timestamp(DSL.literal(refValue)));
+    assertEquals(TIMESTAMP, expr.type());
+    assertEquals(refValue, expr.valueOf(env));
+  }
+
+  private static Instant dateTime2Instant(LocalDateTime dt) {
+    return dt.atZone(ExprTimestampValue.ZONE).toInstant();
+  }
+
+  private static ExprTimestampValue dateTime2ExprTs(LocalDateTime dt) {
+    return new ExprTimestampValue(dateTime2Instant(dt));
+  }
+
+  private static Stream<Arguments> getTestData() {
+    var today = LocalDate.now();
+    // First argument of `TIMESTAMP` function, second argument and expected result value
+    return Stream.of(
+        // STRING and STRING/DATE/TIME/DATETIME/TIMESTAMP
+        Arguments.of("1961-04-12 09:07:00", "2077-12-15 01:48:00",
+            dateTime2ExprTs(LocalDateTime.of(1961, 4, 12, 10, 55, 0))),
+        Arguments.of("1984-02-10 12:20:42", LocalDate.of(2077, 12, 21),
+            dateTime2ExprTs(LocalDateTime.of(1984, 2, 10, 12, 20, 42))),
+        Arguments.of("1961-04-12 09:07:00", LocalTime.of(1, 48),
+            dateTime2ExprTs(LocalDateTime.of(1961, 4, 12, 10, 55, 0))),
+        Arguments.of("2020-12-31 17:30:00", LocalDateTime.of(2077, 12, 21, 12, 20, 42),
+            dateTime2ExprTs(LocalDateTime.of(2021, 1, 1, 5, 50, 42))),
+        Arguments.of("2020-12-31 17:30:00", Instant.ofEpochSecond(42),
+            dateTime2ExprTs(LocalDateTime.of(2020, 12, 31, 17, 30, 42))),
+        // DATE and STRING/DATE/TIME/DATETIME/TIMESTAMP
+        Arguments.of(LocalDate.of(2077, 12, 21), "2077-12-15 01:48:00",
+            dateTime2ExprTs(LocalDateTime.of(2077, 12, 21, 1, 48, 0))),
+        Arguments.of(LocalDate.of(2077, 12, 21), LocalDate.of(1984, 2, 3),
+            dateTime2ExprTs(LocalDateTime.of(2077, 12, 21, 0, 0, 0))),
+        Arguments.of(LocalDate.of(2077, 12, 21), LocalTime.of(22, 33, 44),
+            dateTime2ExprTs(LocalDateTime.of(2077, 12, 21, 22, 33, 44))),
+        Arguments.of(LocalDate.of(2077, 12, 21), LocalDateTime.of(1999, 9, 9, 22, 33, 44),
+            dateTime2ExprTs(LocalDateTime.of(2077, 12, 21, 22, 33, 44))),
+        Arguments.of(LocalDate.of(2077, 12, 21), Instant.ofEpochSecond(42),
+            dateTime2ExprTs(LocalDateTime.of(2077, 12, 21, 0, 0, 42))),
+        // TIME and STRING/DATE/TIME/DATETIME/TIMESTAMP
+        Arguments.of(LocalTime.of(9, 7, 0), "2077-12-15 01:48:00",
+            dateTime2ExprTs(today.atTime(LocalTime.of(10, 55, 0)))),
+        Arguments.of(LocalTime.of(12, 20, 42), LocalDate.of(2077, 12, 21),
+            dateTime2ExprTs(today.atTime(LocalTime.of(12, 20, 42)))),
+        Arguments.of(LocalTime.of(9, 7, 0), LocalTime.of(1, 48),
+            dateTime2ExprTs(today.atTime(LocalTime.of(10, 55, 0)))),
+        Arguments.of(LocalTime.of(17, 30, 0), LocalDateTime.of(2077, 12, 21, 12, 20, 42),
+            dateTime2ExprTs(today.plusDays(1).atTime(LocalTime.of(5, 50, 42)))),
+        Arguments.of(LocalTime.of(17, 30, 0), Instant.ofEpochSecond(42),
+            dateTime2ExprTs(today.atTime(LocalTime.of(17, 30, 42)))),
+        // DATETIME and STRING/DATE/TIME/DATETIME/TIMESTAMP
+        Arguments.of(LocalDateTime.of(1961, 4, 12, 9, 7, 0), "2077-12-15 01:48:00",
+            dateTime2ExprTs(LocalDateTime.of(1961, 4, 12, 10, 55, 0))),
+        Arguments.of(LocalDateTime.of(1984, 2, 10, 12, 20, 42), LocalDate.of(2077, 12, 21),
+            dateTime2ExprTs(LocalDateTime.of(1984, 2, 10, 12, 20, 42))),
+        Arguments.of(LocalDateTime.of(1961, 4, 12, 9, 7, 0), LocalTime.of(1, 48),
+            dateTime2ExprTs(LocalDateTime.of(1961, 4, 12, 10, 55, 0))),
+        Arguments.of(LocalDateTime.of(2020, 12, 31, 17, 30, 0),
+            LocalDateTime.of(2077, 12, 21, 12, 20, 42),
+            dateTime2ExprTs(LocalDateTime.of(2021, 1, 1, 5, 50, 42))),
+        Arguments.of(LocalDateTime.of(2020, 12, 31, 17, 30, 0), Instant.ofEpochSecond(42),
+            dateTime2ExprTs(LocalDateTime.of(2020, 12, 31, 17, 30, 42))),
+        // TIMESTAMP and STRING/DATE/TIME/DATETIME/TIMESTAMP
+        Arguments.of(dateTime2Instant(LocalDateTime.of(1961, 4, 12, 9, 7, 0)),
+            "2077-12-15 01:48:00",
+            dateTime2ExprTs(LocalDateTime.of(1961, 4, 12, 10, 55, 0))),
+        Arguments.of(dateTime2Instant(LocalDateTime.of(1984, 2, 10, 12, 20, 42)),
+            LocalDate.of(2077, 12, 21),
+            dateTime2ExprTs(LocalDateTime.of(1984, 2, 10, 12, 20, 42))),
+        Arguments.of(dateTime2Instant(LocalDateTime.of(1961, 4, 12, 9, 7, 0)),
+            LocalTime.of(1, 48),
+            dateTime2ExprTs(LocalDateTime.of(1961, 4, 12, 10, 55, 0))),
+        Arguments.of(dateTime2Instant(LocalDateTime.of(2020, 12, 31, 17, 30, 0)),
+            LocalDateTime.of(2077, 12, 21, 12, 20, 42),
+            dateTime2ExprTs(LocalDateTime.of(2021, 1, 1, 5, 50, 42))),
+        Arguments.of(dateTime2Instant(LocalDateTime.of(2020, 12, 31, 17, 30, 0)),
+            Instant.ofEpochSecond(42),
+            dateTime2ExprTs(LocalDateTime.of(2020, 12, 31, 17, 30, 42)))
+    );
+  }
+
+  @ParameterizedTest
+  @MethodSource("getTestData")
+  public void timestamp_with_two_args(Object arg1, Object arg2, ExprTimestampValue expected) {
+    var expr = dsl.timestamp(
+        DSL.literal(ExprValueUtils.fromObjectValue(arg1)),
+        DSL.literal(ExprValueUtils.fromObjectValue(arg2)));
+    assertEquals(TIMESTAMP, expr.type());
+    assertEquals(expected, expr.valueOf(env));
+  }
+}

From 5e6423b54b7fdf9dc88c6b3402923d71d6dbe79b Mon Sep 17 00:00:00 2001
From: Yury-Fridlyand <yuryf@bitquilltech.com>
Date: Thu, 20 Oct 2022 15:45:37 -0700
Subject: [PATCH 08/14] Update docs.

Signed-off-by: Yury-Fridlyand <yuryf@bitquilltech.com>
---
 docs/user/dql/functions.rst          |  28 +++---
 docs/user/ppl/functions/datetime.rst | 133 ++++-----------------------
 2 files changed, 33 insertions(+), 128 deletions(-)

diff --git a/docs/user/dql/functions.rst b/docs/user/dql/functions.rst
index 3e363efb820..f094fba48d5 100644
--- a/docs/user/dql/functions.rst
+++ b/docs/user/dql/functions.rst
@@ -1172,9 +1172,9 @@ Argument type: DATETIME/STRING
 
 Return type map:
 
-DATETIME, STRING -> DATETIME
+(DATETIME, STRING) -> DATETIME
 
-DATETIME -> DATETIME
+(DATETIME) -> DATETIME
 
 Example::
 
@@ -2087,6 +2087,7 @@ Example::
     | 2007-02-28 13:39:40                     |
     +-----------------------------------------+
 
+
 TIME
 ----
 
@@ -2139,21 +2140,26 @@ TIMESTAMP
 Description
 >>>>>>>>>>>
 
-Usage: timestamp(expr) construct a timestamp type with the input string expr as an timestamp. If the argument is of date/datetime/timestamp type, cast expr to timestamp type with default timezone UTC.
+Usage: timestamp(expr) constructs a timestamp type with the input string `expr` as an timestamp. If the argument is not a string, it casts `expr` to timestamp type with default timezone UTC. If argument is a time, it applied to today's date before cast.
+With two arguments `timestamp(expr1, expr2)` adds the time expression `expr2` to the date or datetime expression `expr1` and returns the result as a timestamp value.
 
-Argument type: STRING/DATE/DATETIME/TIMESTAMP
+Argument type: STRING/DATE/TIME/DATETIME/TIMESTAMP
+
+Return type map:
 
-Return type: TIMESTAMP
+(STRING/DATE/TIME/DATETIME/TIMESTAMP) -> TIMESTAMP
+
+(STRING/DATE/TIME/DATETIME/TIMESTAMP, STRING/DATE/TIME/DATETIME/TIMESTAMP) -> TIMESTAMP
 
 Example::
 
-    >od SELECT TIMESTAMP('2020-08-26 13:49:00')
+    os> SELECT TIMESTAMP('2020-08-26 13:49:00'), TIMESTAMP('2020-08-26 13:49:00', TIME('12:15:42'))
     fetched rows / total rows = 1/1
-    +------------------------------------+
-    | TIMESTAMP('2020-08-26 13:49:00')   |
-    |------------------------------------|
-    | TIMESTAMP '2020-08-26 13:49:00     |
-    +------------------------------------+
+    +------------------------------------+------------------------------------------------------+
+    | TIMESTAMP('2020-08-26 13:49:00')   | TIMESTAMP('2020-08-26 13:49:00', TIME('12:15:42'))   |
+    |------------------------------------+------------------------------------------------------|
+    | 2020-08-26 13:49:00                | 2020-08-27 02:04:42                                  |
+    +------------------------------------+------------------------------------------------------+
 
 
 TO_DAYS
diff --git a/docs/user/ppl/functions/datetime.rst b/docs/user/ppl/functions/datetime.rst
index ae893a5e8b0..a66e8c4efbb 100644
--- a/docs/user/ppl/functions/datetime.rst
+++ b/docs/user/ppl/functions/datetime.rst
@@ -234,111 +234,6 @@ Example::
     +-------------------------------------------------------+
 
 
-CURDATE
--------
-
-Description
->>>>>>>>>>>
-
-Returns the current time as a value in 'YYYY-MM-DD'.
-CURDATE() returns the time at which it executes as `SYSDATE() <#sysdate>`_ does.
-
-Return type: DATE
-
-Specification: CURDATE() -> DATE
-
-Example::
-
-    > source=people | eval `CURDATE()` = CURDATE() | fields `CURDATE()`
-    fetched rows / total rows = 1/1
-    +-------------+
-    | CURDATE()   |
-    |-------------|
-    | 2022-08-02  |
-    +-------------+
-
-
-CURRENT_DATE
-------------
-
-Description
->>>>>>>>>>>
-
-`CURRENT_DATE()` are synonyms for `CURDATE() <#curdate>`_.
-
-Example::
-
-    > source=people | eval `CURRENT_DATE()` = CURRENT_DATE() | fields `CURRENT_DATE()`
-    fetched rows / total rows = 1/1
-    +------------------+
-    | CURRENT_DATE()   |
-    |------------------+
-    | 2022-08-02       |
-    +------------------+
-
-
-CURRENT_TIME
-------------
-
-Description
->>>>>>>>>>>
-
-`CURRENT_TIME()` are synonyms for `CURTIME() <#curtime>`_.
-
-Example::
-
-    > source=people | eval `CURRENT_TIME()` = CURRENT_TIME() | fields `CURRENT_TIME()`
-    fetched rows / total rows = 1/1
-    +------------------+
-    | CURRENT_TIME()   |
-    |------------------+
-    | 15:39:05         |
-    +------------------+
-
-
-CURRENT_TIMESTAMP
------------------
-
-Description
->>>>>>>>>>>
-
-`CURRENT_TIMESTAMP()` are synonyms for `NOW() <#now>`_.
-
-Example::
-
-    > source=people | eval `CURRENT_TIMESTAMP()` = CURRENT_TIMESTAMP() | fields `CURRENT_TIMESTAMP()`
-    fetched rows / total rows = 1/1
-    +-----------------------+
-    | CURRENT_TIMESTAMP()   |
-    |-----------------------+
-    | 2022-08-02 15:54:19   |
-    +-----------------------+
-
-
-CURTIME
--------
-
-Description
->>>>>>>>>>>
-
-Returns the current time as a value in 'hh:mm:ss'.
-CURTIME() returns the time at which the statement began to execute as `NOW() <#now>`_ does.
-
-Return type: TIME
-
-Specification: CURTIME() -> TIME
-
-Example::
-
-    > source=people | eval `value_1` = CURTIME(), `value_2` = CURTIME() | fields `value_1`, `value_2`
-    fetched rows / total rows = 1/1
-    +-----------+-----------+
-    | value_1   | value_2   |
-    |-----------+-----------|
-    | 15:39:05  | 15:39:05  |
-    +-----------+-----------+
-
-
 DATE
 ----
 
@@ -516,7 +411,6 @@ Example::
     +-----------------------------------------------+----------------------------------------------------------------+
 
 
-
 DATETIME
 --------
 
@@ -529,9 +423,9 @@ Argument type: DATETIME/STRING
 
 Return type map:
 
-DATETIME, STRING -> DATETIME
+(DATETIME, STRING) -> DATETIME
 
-DATETIME -> DATETIME
+(DATETIME) -> DATETIME
 
 
 Converting datetime with timezone to the second argument timezone.
@@ -1281,21 +1175,26 @@ TIMESTAMP
 Description
 >>>>>>>>>>>
 
-Usage: timestamp(expr) construct a timestamp type with the input string expr as an timestamp. If the argument is of date/datetime/timestamp type, cast expr to timestamp type with default timezone UTC.
+Usage: timestamp(expr) constructs a timestamp type with the input string `expr` as an timestamp. If the argument is not a string, it casts `expr` to timestamp type with default timezone UTC. If argument is a time, it applied to today's date before cast.
+With two arguments `timestamp(expr1, expr2)` adds the time expression `expr2` to the date or datetime expression `expr1` and returns the result as a timestamp value.
 
-Argument type: STRING/DATE/DATETIME/TIMESTAMP
+Argument type: STRING/DATE/TIME/DATETIME/TIMESTAMP
+
+Return type map:
+
+(STRING/DATE/TIME/DATETIME/TIMESTAMP) -> TIMESTAMP
 
-Return type: TIMESTAMP
+(STRING/DATE/TIME/DATETIME/TIMESTAMP, STRING/DATE/TIME/DATETIME/TIMESTAMP) -> TIMESTAMP
 
 Example::
 
-    >od source=people | eval `TIMESTAMP('2020-08-26 13:49:00')` = TIMESTAMP('2020-08-26 13:49:00') | fields `TIMESTAMP('2020-08-26 13:49:00')`
+    os> source=people | eval `TIMESTAMP('2020-08-26 13:49:00')` = TIMESTAMP('2020-08-26 13:49:00'), `TIMESTAMP('2020-08-26 13:49:00', TIME('12:15:42'))` = TIMESTAMP('2020-08-26 13:49:00', TIME('12:15:42')) | fields `TIMESTAMP('2020-08-26 13:49:00')`, `TIMESTAMP('2020-08-26 13:49:00', TIME('12:15:42'))`
     fetched rows / total rows = 1/1
-    +------------------------------------+
-    | TIMESTAMP('2020-08-26 13:49:00')   |
-    |------------------------------------|
-    | TIMESTAMP '2020-08-26 13:49:00     |
-    +------------------------------------+
+    +------------------------------------+------------------------------------------------------+
+    | TIMESTAMP('2020-08-26 13:49:00')   | TIMESTAMP('2020-08-26 13:49:00', TIME('12:15:42'))   |
+    |------------------------------------+------------------------------------------------------|
+    | 2020-08-26 13:49:00                | 2020-08-27 02:04:42                                  |
+    +------------------------------------+------------------------------------------------------+
 
 
 TO_DAYS

From e257d5c4af1c7e5e0a7418dcec0906032368db68 Mon Sep 17 00:00:00 2001
From: Yury-Fridlyand <yuryf@bitquilltech.com>
Date: Thu, 20 Oct 2022 15:51:55 -0700
Subject: [PATCH 09/14] Minor checkstyle fixes.

Signed-off-by: Yury-Fridlyand <yuryf@bitquilltech.com>
---
 .../sql/expression/datetime/DateTimeFunction.java           | 1 -
 .../opensearch/sql/expression/datetime/TimestampTest.java   | 6 ++++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java b/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
index 16c193ecbe7..c9c92b511a0 100644
--- a/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
+++ b/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
@@ -599,7 +599,6 @@ private DefaultFunctionResolver time_to_sec() {
   /**
    * Extracts the timestamp of a date and time value.
    * Input strings may contain a timestamp only in format 'yyyy-MM-dd HH:mm:ss[.SSSSSSSSS]'
-   *
    * STRING/DATE/TIME/DATETIME/TIMESTAMP -> TIMESTAMP
    * STRING/DATE/TIME/DATETIME/TIMESTAMP, STRING/DATE/TIME/DATETIME/TIMESTAMP -> TIMESTAMP
    */
diff --git a/core/src/test/java/org/opensearch/sql/expression/datetime/TimestampTest.java b/core/src/test/java/org/opensearch/sql/expression/datetime/TimestampTest.java
index 68e7e59897c..66c9f345cfa 100644
--- a/core/src/test/java/org/opensearch/sql/expression/datetime/TimestampTest.java
+++ b/core/src/test/java/org/opensearch/sql/expression/datetime/TimestampTest.java
@@ -174,6 +174,12 @@ private static Stream<Arguments> getTestData() {
     );
   }
 
+  /**
+   * Test `TIMESTAMP` function which takes 2 arguments with input of different types.
+   * @param arg1 First argument to be passed to `TIMESTAMP` function.
+   * @param arg2 Second argument to be passed to `TIMESTAMP` function.
+   * @param expected The expected result.
+   */
   @ParameterizedTest
   @MethodSource("getTestData")
   public void timestamp_with_two_args(Object arg1, Object arg2, ExprTimestampValue expected) {

From 5e8620203c86f2d5c9a45011ec9a1f093207e320 Mon Sep 17 00:00:00 2001
From: Yury-Fridlyand <yuryf@bitquilltech.com>
Date: Mon, 31 Oct 2022 18:42:24 -0700
Subject: [PATCH 10/14] Make function to throw an exception on incorrect input.

Signed-off-by: Yury-Fridlyand <yuryf@bitquilltech.com>
---
 .../expression/datetime/DateTimeFunction.java |  9 +----
 .../expression/datetime/TimestampTest.java    | 37 ++++++++++---------
 2 files changed, 22 insertions(+), 24 deletions(-)

diff --git a/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java b/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
index c9c92b511a0..d0b7ead496b 100644
--- a/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
+++ b/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
@@ -1187,14 +1187,9 @@ private ExprValue exprTime(ExprValue exprValue) {
    */
   private ExprValue exprTimestamp(ExprValue exprValue) {
     if (exprValue instanceof ExprStringValue) {
-      try {
-        return new ExprTimestampValue(exprValue.stringValue());
-      } catch (SemanticCheckException ignored) {
-        return ExprNullValue.of();
-      }
-    } else {
-      return new ExprTimestampValue(exprValue.timestampValue());
+      return new ExprTimestampValue(exprValue.stringValue());
     }
+    return new ExprTimestampValue(exprValue.timestampValue());
   }
 
   /**
diff --git a/core/src/test/java/org/opensearch/sql/expression/datetime/TimestampTest.java b/core/src/test/java/org/opensearch/sql/expression/datetime/TimestampTest.java
index 66c9f345cfa..ad61ebd9956 100644
--- a/core/src/test/java/org/opensearch/sql/expression/datetime/TimestampTest.java
+++ b/core/src/test/java/org/opensearch/sql/expression/datetime/TimestampTest.java
@@ -6,6 +6,7 @@
 package org.opensearch.sql.expression.datetime;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.opensearch.sql.data.type.ExprCoreType.TIMESTAMP;
 
 import java.time.Instant;
@@ -17,13 +18,14 @@
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.CsvSource;
 import org.junit.jupiter.params.provider.MethodSource;
 import org.mockito.Mock;
 import org.mockito.junit.jupiter.MockitoExtension;
-import org.opensearch.sql.data.model.ExprNullValue;
 import org.opensearch.sql.data.model.ExprTimestampValue;
 import org.opensearch.sql.data.model.ExprValue;
 import org.opensearch.sql.data.model.ExprValueUtils;
+import org.opensearch.sql.exception.SemanticCheckException;
 import org.opensearch.sql.expression.DSL;
 import org.opensearch.sql.expression.Expression;
 import org.opensearch.sql.expression.ExpressionTestBase;
@@ -47,22 +49,23 @@ public void timestamp_one_arg_string() {
         expr.valueOf(env).datetimeValue());
   }
 
-  @Test
-  public void timestamp_one_arg_string_invalid_format() {
-    // Feb 30th
-    var expr = dsl.timestamp(DSL.literal("1984-02-30 12:20:42"));
-    assertEquals(TIMESTAMP, expr.type());
-    assertEquals(ExprNullValue.of(), expr.valueOf(env));
-
-    // 24:00:00
-    expr = dsl.timestamp(DSL.literal("1984-02-10 24:00:00"));
-    assertEquals(TIMESTAMP, expr.type());
-    assertEquals(ExprNullValue.of(), expr.valueOf(env));
-
-    // 2 digit year
-    expr = dsl.timestamp(DSL.literal("84-02-10 12:20:42"));
-    assertEquals(TIMESTAMP, expr.type());
-    assertEquals(ExprNullValue.of(), expr.valueOf(env));
+  /**
+   * Check that `TIMESTAMP` function throws an exception on incorrect string input.
+   * @param value A value.
+   * @param testName A test name.
+   */
+  @ParameterizedTest(name = "{1}")
+  @CsvSource({
+      "1984-02-30 12:20:42, Feb 30th",
+      "1984-02-10 24:00:00, 24:00:00",
+      "84-02-10 12:20:42, 2 digit year"
+  })
+  public void timestamp_one_arg_string_invalid_format(String value, String testName) {
+    // exception thrown from ExprTimestampValue(String) CTOR
+    var exception = assertThrows(SemanticCheckException.class,
+        () -> dsl.timestamp(DSL.literal(value)).valueOf(env));
+    assertEquals(String.format("timestamp:%s in unsupported format, please "
+        + "use yyyy-MM-dd HH:mm:ss[.SSSSSSSSS]", value), exception.getMessage());
   }
 
   @Test

From 86524aac8f053072ee105c76a93b72a7e7f18fff Mon Sep 17 00:00:00 2001
From: Yury-Fridlyand <yury.fridlyand@improving.com>
Date: Mon, 12 Dec 2022 19:23:21 -0800
Subject: [PATCH 11/14] Fix rebasing errors.

Signed-off-by: Yury-Fridlyand <yury.fridlyand@improving.com>
---
 .../sql/data/model/ExprTimeValue.java         | 17 ------
 .../sql/data/model/DateTimeValueTest.java     | 21 +++++--
 .../expression/datetime/DateTimeTestBase.java | 28 +--------
 .../sql/sql/DateTimeFunctionIT.java           | 19 ++++++
 ppl/src/main/antlr/OpenSearchPPLParser.g4     | 58 +++++++++++++++----
 sql/src/main/antlr/OpenSearchSQLParser.g4     |  9 ---
 6 files changed, 86 insertions(+), 66 deletions(-)

diff --git a/core/src/main/java/org/opensearch/sql/data/model/ExprTimeValue.java b/core/src/main/java/org/opensearch/sql/data/model/ExprTimeValue.java
index a1019acdbbb..d77a2615d26 100644
--- a/core/src/main/java/org/opensearch/sql/data/model/ExprTimeValue.java
+++ b/core/src/main/java/org/opensearch/sql/data/model/ExprTimeValue.java
@@ -13,9 +13,7 @@
 import java.time.LocalDate;
 import java.time.LocalDateTime;
 import java.time.LocalTime;
-import java.time.ZoneId;
 import java.time.ZonedDateTime;
-import java.time.format.DateTimeFormatter;
 import java.time.format.DateTimeParseException;
 import java.util.Objects;
 import lombok.RequiredArgsConstructor;
@@ -72,21 +70,6 @@ public Instant timestampValue(FunctionProperties functionProperties) {
         .toInstant();
   }
 
-  @Override
-  public LocalDate dateValue() {
-    return LocalDate.now();
-  }
-
-  @Override
-  public LocalDateTime datetimeValue() {
-    return LocalDateTime.of(dateValue(), timeValue());
-  }
-
-  @Override
-  public Instant timestampValue() {
-    return ZonedDateTime.of(dateValue(), timeValue(), ZoneId.systemDefault()).toInstant();
-  }
-
   @Override
   public String toString() {
     return String.format("TIME '%s'", value());
diff --git a/core/src/test/java/org/opensearch/sql/data/model/DateTimeValueTest.java b/core/src/test/java/org/opensearch/sql/data/model/DateTimeValueTest.java
index 4fc4a7d563f..a335478e193 100644
--- a/core/src/test/java/org/opensearch/sql/data/model/DateTimeValueTest.java
+++ b/core/src/test/java/org/opensearch/sql/data/model/DateTimeValueTest.java
@@ -32,10 +32,23 @@ public void timeValueInterfaceTest() {
     assertEquals(TIME, timeValue.type());
 
     assertEquals(LocalTime.parse("01:01:01"), timeValue.timeValue());
-    assertEquals(LocalDate.now(), timeValue.dateValue());
-    assertEquals(LocalDate.now().atTime(1, 1, 1), timeValue.datetimeValue());
-    assertEquals(ZonedDateTime.of(LocalTime.parse("01:01:01").atDate(LocalDate.now()),
-        ZoneId.systemDefault()).toInstant(), timeValue.timestampValue());
+    // It is prohibited to acquire values which include date part from `ExprTimeValue`
+    // without a FunctionProperties object
+    var exception = assertThrows(ExpressionEvaluationException.class, timeValue::dateValue);
+    assertEquals("invalid to get dateValue from value of type TIME", exception.getMessage());
+    exception = assertThrows(ExpressionEvaluationException.class, timeValue::datetimeValue);
+    assertEquals("invalid to get datetimeValue from value of type TIME", exception.getMessage());
+    exception = assertThrows(ExpressionEvaluationException.class, timeValue::timestampValue);
+    assertEquals("invalid to get timestampValue from value of type TIME", exception.getMessage());
+
+    var functionProperties = new FunctionProperties();
+    var today = LocalDate.now(functionProperties.getQueryStartClock());
+
+    assertEquals(today, timeValue.dateValue(functionProperties));
+    assertEquals(today.atTime(1, 1, 1), timeValue.datetimeValue(functionProperties));
+    assertEquals(ZonedDateTime.of(LocalTime.parse("01:01:01").atDate(today),
+        ExprTimestampValue.ZONE).toInstant(), timeValue.timestampValue(functionProperties));
+
     assertEquals("01:01:01", timeValue.value());
     assertEquals("TIME '01:01:01'", timeValue.toString());
     exception = assertThrows(ExpressionEvaluationException.class,
diff --git a/core/src/test/java/org/opensearch/sql/expression/datetime/DateTimeTestBase.java b/core/src/test/java/org/opensearch/sql/expression/datetime/DateTimeTestBase.java
index 08004a84dc4..38beaad1315 100644
--- a/core/src/test/java/org/opensearch/sql/expression/datetime/DateTimeTestBase.java
+++ b/core/src/test/java/org/opensearch/sql/expression/datetime/DateTimeTestBase.java
@@ -6,7 +6,6 @@
 package org.opensearch.sql.expression.datetime;
 
 import static org.opensearch.sql.data.model.ExprValueUtils.fromObjectValue;
-import static org.opensearch.sql.data.type.ExprCoreType.DOUBLE;
 
 import java.time.Instant;
 import java.time.LocalDate;
@@ -82,17 +81,6 @@ protected String fromUnixTime(Double value, String format) {
         .valueOf().stringValue();
   }
 
-  protected FunctionExpression addtime(Expression date, Expression interval) {
-    var func = functionRepository.resolve(new FunctionSignature(new FunctionName("addtime"),
-        List.of(date.type(), interval.type())));
-    return (FunctionExpression)func.apply(List.of(date, interval));
-  }
-
-  protected ExprValue addtime(Temporal first, Temporal second) {
-    return addtime(DSL.literal(fromObjectValue(first)), DSL.literal(fromObjectValue(second)))
-        .valueOf(null);
-  }
-
   protected FunctionExpression maketime(Expression hour, Expression minute, Expression second) {
     return (FunctionExpression)
         functionRepository.compile(
@@ -179,18 +167,8 @@ protected Double unixTimeStampOf(LocalDateTime value) {
         .valueOf().doubleValue();
   }
 
-  protected FunctionExpression subtime(Expression date, Expression interval) {
-    var func = functionRepository.resolve(new FunctionSignature(new FunctionName("subtime"),
-        List.of(date.type(), interval.type())));
-    return (FunctionExpression)func.apply(List.of(date, interval));
-  }
-
-  protected ExprValue subtime(Temporal first, Temporal second) {
-    return subtime(DSL.literal(fromObjectValue(first)), DSL.literal(fromObjectValue(second)))
-        .valueOf(null);
-  }
-
-  protected ExprValue eval(Expression expression) {
-    return expression.valueOf(env);
+  protected Double unixTimeStampOf(Instant value) {
+    return unixTimeStampOf(DSL.literal(new ExprTimestampValue(value)))
+        .valueOf().doubleValue();
   }
 }
diff --git a/integ-test/src/test/java/org/opensearch/sql/sql/DateTimeFunctionIT.java b/integ-test/src/test/java/org/opensearch/sql/sql/DateTimeFunctionIT.java
index fd87a6d4e3f..f10596e21c3 100644
--- a/integ-test/src/test/java/org/opensearch/sql/sql/DateTimeFunctionIT.java
+++ b/integ-test/src/test/java/org/opensearch/sql/sql/DateTimeFunctionIT.java
@@ -826,6 +826,25 @@ public void testUnixTimeStamp() throws IOException {
   }
 
   @Test
+  public void testPeriodAdd() throws IOException {
+    var result = executeQuery(
+        "select PERIOD_ADD(200801, 2) as f1, PERIOD_ADD(200801, -12) as f2");
+    verifySchema(result,
+        schema("PERIOD_ADD(200801, 2)", "f1", "integer"),
+        schema("PERIOD_ADD(200801, -12)", "f2", "integer"));
+    verifyDataRows(result, rows(200803, 200701));
+  }
+
+  @Test
+  public void testPeriodDiff() throws IOException {
+    var result = executeQuery(
+        "select PERIOD_DIFF(200802, 200703) as f1, PERIOD_DIFF(200802, 201003) as f2");
+    verifySchema(result,
+        schema("PERIOD_DIFF(200802, 200703)", "f1", "integer"),
+        schema("PERIOD_DIFF(200802, 201003)", "f2", "integer"));
+    verifyDataRows(result, rows(11, -25));
+  }
+
   public void testAddTime() throws IOException {
     var result = executeQuery("SELECT"
         + " ADDTIME(DATE('2008-12-12'), DATE('2008-11-15')) AS `'2008-12-12' + 0`,"
diff --git a/ppl/src/main/antlr/OpenSearchPPLParser.g4 b/ppl/src/main/antlr/OpenSearchPPLParser.g4
index edc33983a4a..9cb539cfbaa 100644
--- a/ppl/src/main/antlr/OpenSearchPPLParser.g4
+++ b/ppl/src/main/antlr/OpenSearchPPLParser.g4
@@ -428,17 +428,53 @@ trigonometricFunctionName
     ;
 
 dateAndTimeFunctionBase
-    : ADDDATE | ADDTIME | CONVERT_TZ | DATE | DATE_ADD | DATE_FORMAT | DATE_SUB
-    | DATETIME | DAY | DAYNAME | DAYOFMONTH | DAYOFWEEK | DAYOFYEAR | FROM_DAYS | FROM_UNIXTIME
-    | HOUR | MAKEDATE | MAKETIME | MICROSECOND | MINUTE | MONTH | MONTHNAME
-    | QUARTER | SECOND | SUBDATE | SUBTIME | SYSDATE | TIME | TIME_TO_SEC
-    | TIMESTAMP | TO_DAYS | UNIX_TIMESTAMP | WEEK | YEAR
-    ;
-
-// Functions which value could be cached in scope of a single query
-constantFunctionName
-    : datetimeConstantLiteral
-    | CURDATE | CURTIME | NOW
+    : ADDDATE
+    | ADDTIME
+    | CONVERT_TZ
+    | CURRENT_DATE
+    | CURRENT_TIME
+    | CURRENT_TIMESTAMP
+    | DATE
+    | DATE_ADD
+    | DATE_FORMAT
+    | DATE_SUB
+    | DATETIME
+    | DAY
+    | DAYNAME
+    | DAYOFMONTH
+    | DAYOFWEEK
+    | DAYOFYEAR
+    | CURDATE
+    | CURTIME
+    | FROM_DAYS
+    | FROM_UNIXTIME
+    | HOUR
+    | LOCALTIME
+    | LOCALTIMESTAMP
+    | MAKEDATE
+    | MAKETIME
+    | MICROSECOND
+    | MINUTE
+    | MONTH
+    | MONTHNAME
+    | NOW
+    | PERIOD_ADD
+    | PERIOD_DIFF
+    | QUARTER
+    | SECOND
+    | SUBDATE
+    | SUBTIME
+    | SYSDATE
+    | TIME
+    | TIME_TO_SEC
+    | TIMESTAMP
+    | TO_DAYS
+    | UNIX_TIMESTAMP
+    | UTC_DATE
+    | UTC_TIME
+    | UTC_TIMESTAMP
+    | WEEK
+    | YEAR
     ;
 
 /** condition function return boolean value */
diff --git a/sql/src/main/antlr/OpenSearchSQLParser.g4 b/sql/src/main/antlr/OpenSearchSQLParser.g4
index 3076727b55e..1598e7676cb 100644
--- a/sql/src/main/antlr/OpenSearchSQLParser.g4
+++ b/sql/src/main/antlr/OpenSearchSQLParser.g4
@@ -411,15 +411,6 @@ trigonometricFunctionName
     ;
 
 dateTimeFunctionName
-    : ADDDATE | ADDTIME | CONVERT_TZ | DATE | DATE_ADD | DATE_FORMAT | DATE_SUB
-    | DATETIME | DAY | DAYNAME | DAYOFMONTH | DAYOFWEEK | DAYOFYEAR | FROM_DAYS | FROM_UNIXTIME
-    | HOUR | MAKEDATE | MAKETIME | MICROSECOND | MINUTE | MONTH | MONTHNAME
-    | QUARTER | SECOND | SUBDATE | SUBTIME | SYSDATE | TIME | TIME_TO_SEC
-    | TIMESTAMP | TO_DAYS | UNIX_TIMESTAMP | WEEK | YEAR
-    ;
-
-// Functions which value could be cached in scope of a single query
-constantFunctionName
     : datetimeConstantLiteral
     | ADDDATE
     | ADDTIME

From 84a1d4d868aab4090c45104a1e04dc28034b64ab Mon Sep 17 00:00:00 2001
From: Yury-Fridlyand <yury.fridlyand@improving.com>
Date: Mon, 12 Dec 2022 19:30:34 -0800
Subject: [PATCH 12/14] Rework to use `FunctionProperties`.

Signed-off-by: Yury-Fridlyand <yury.fridlyand@improving.com>
---
 .../org/opensearch/sql/expression/DSL.java    |   7 +-
 .../expression/datetime/DateTimeFunction.java | 243 +++++++++++-------
 .../opensearch/sql/utils/DateTimeUtils.java   |  11 +
 .../expression/datetime/TimestampTest.java    |  41 ++-
 docs/user/dql/functions.rst                   |  39 ++-
 docs/user/ppl/functions/datetime.rst          | 144 ++++++++++-
 6 files changed, 357 insertions(+), 128 deletions(-)

diff --git a/core/src/main/java/org/opensearch/sql/expression/DSL.java b/core/src/main/java/org/opensearch/sql/expression/DSL.java
index f5fd1e33153..1373f46273e 100644
--- a/core/src/main/java/org/opensearch/sql/expression/DSL.java
+++ b/core/src/main/java/org/opensearch/sql/expression/DSL.java
@@ -387,7 +387,12 @@ public static FunctionExpression time_to_sec(Expression... expressions) {
   }
 
   public static FunctionExpression timestamp(Expression... expressions) {
-    return compile(FunctionProperties.None, BuiltinFunctionName.TIMESTAMP, expressions);
+    return timestamp(FunctionProperties.None, expressions);
+  }
+
+  public static FunctionExpression timestamp(FunctionProperties functionProperties,
+                                             Expression... expressions) {
+    return compile(functionProperties, BuiltinFunctionName.TIMESTAMP, expressions);
   }
 
   public static FunctionExpression date_format(Expression... expressions) {
diff --git a/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java b/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
index d0b7ead496b..f0d1f208810 100644
--- a/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
+++ b/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
@@ -128,6 +128,7 @@ public void register(BuiltinFunctionRepository repository) {
     repository.register(second());
     repository.register(subdate());
     repository.register(subtime());
+    repository.register(sysdate());
     repository.register(time());
     repository.register(time_to_sec());
     repository.register(timestamp());
@@ -249,22 +250,38 @@ private DefaultFunctionResolver adddate() {
    */
   private DefaultFunctionResolver addtime() {
     return define(BuiltinFunctionName.ADDTIME.getName(),
-        impl(nullMissingHandling(DateTimeFunction::exprAddTime), TIME, TIME, TIME),
-        impl(nullMissingHandling(DateTimeFunction::exprAddTime), TIME, TIME, DATE),
-        impl(nullMissingHandling(DateTimeFunction::exprAddTime), TIME, TIME, DATETIME),
-        impl(nullMissingHandling(DateTimeFunction::exprAddTime), TIME, TIME, TIMESTAMP),
-        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, DATETIME, TIME),
-        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, DATETIME, DATE),
-        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, DATETIME, DATETIME),
-        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, DATETIME, TIMESTAMP),
-        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, DATE, TIME),
-        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, DATE, DATE),
-        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, DATE, DATETIME),
-        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, DATE, TIMESTAMP),
-        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, TIMESTAMP, TIME),
-        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, TIMESTAMP, DATE),
-        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, TIMESTAMP, DATETIME),
-        impl(nullMissingHandling(DateTimeFunction::exprAddTime), DATETIME, TIMESTAMP, TIMESTAMP)
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
+            TIME, TIME, TIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
+            TIME, TIME, DATE),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
+            TIME, TIME, DATETIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
+            TIME, TIME, TIMESTAMP),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
+            DATETIME, DATETIME, TIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
+            DATETIME, DATETIME, DATE),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
+            DATETIME, DATETIME, DATETIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
+            DATETIME, DATETIME, TIMESTAMP),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
+            DATETIME, DATE, TIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
+            DATETIME, DATE, DATE),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
+            DATETIME, DATE, DATETIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
+            DATETIME, DATE, TIMESTAMP),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
+            DATETIME, TIMESTAMP, TIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
+            DATETIME, TIMESTAMP, DATE),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
+            DATETIME, TIMESTAMP, DATETIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprAddTime),
+            DATETIME, TIMESTAMP, TIMESTAMP)
     );
   }
 
@@ -551,22 +568,38 @@ private DefaultFunctionResolver subdate() {
    */
   private DefaultFunctionResolver subtime() {
     return define(BuiltinFunctionName.SUBTIME.getName(),
-        impl(nullMissingHandling(DateTimeFunction::exprSubTime), TIME, TIME, TIME),
-        impl(nullMissingHandling(DateTimeFunction::exprSubTime), TIME, TIME, DATE),
-        impl(nullMissingHandling(DateTimeFunction::exprSubTime), TIME, TIME, DATETIME),
-        impl(nullMissingHandling(DateTimeFunction::exprSubTime), TIME, TIME, TIMESTAMP),
-        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, DATETIME, TIME),
-        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, DATETIME, DATE),
-        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, DATETIME, DATETIME),
-        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, DATETIME, TIMESTAMP),
-        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, DATE, TIME),
-        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, DATE, DATE),
-        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, DATE, DATETIME),
-        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, DATE, TIMESTAMP),
-        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, TIMESTAMP, TIME),
-        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, TIMESTAMP, DATE),
-        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, TIMESTAMP, DATETIME),
-        impl(nullMissingHandling(DateTimeFunction::exprSubTime), DATETIME, TIMESTAMP, TIMESTAMP)
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
+            TIME, TIME, TIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
+            TIME, TIME, DATE),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
+            TIME, TIME, DATETIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
+            TIME, TIME, TIMESTAMP),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
+            DATETIME, DATETIME, TIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
+            DATETIME, DATETIME, DATE),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
+            DATETIME, DATETIME, DATETIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
+            DATETIME, DATETIME, TIMESTAMP),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
+            DATETIME, DATE, TIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
+            DATETIME, DATE, DATE),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
+            DATETIME, DATE, DATETIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
+            DATETIME, DATE, TIMESTAMP),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
+            DATETIME, TIMESTAMP, TIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
+            DATETIME, TIMESTAMP, DATE),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
+            DATETIME, TIMESTAMP, DATETIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprSubTime),
+            DATETIME, TIMESTAMP, TIMESTAMP)
     );
   }
 
@@ -604,39 +637,65 @@ private DefaultFunctionResolver time_to_sec() {
    */
   private DefaultFunctionResolver timestamp() {
     return define(BuiltinFunctionName.TIMESTAMP.getName(),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestamp), TIMESTAMP, STRING),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestamp), TIMESTAMP, DATE),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestamp), TIMESTAMP, TIME),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestamp), TIMESTAMP, DATETIME),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestamp), TIMESTAMP, TIMESTAMP),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, STRING, STRING),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, STRING, DATE),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, STRING, TIME),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, STRING, DATETIME),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, STRING, TIMESTAMP),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATE, STRING),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATE, DATE),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATE, TIME),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATE, DATETIME),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATE, TIMESTAMP),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIME, STRING),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIME, DATE),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIME, TIME),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIME, DATETIME),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIME, TIMESTAMP),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATETIME, STRING),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATETIME, DATE),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, DATETIME, TIME),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestamp),
+            TIMESTAMP, STRING),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestamp),
+            TIMESTAMP, DATE),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestamp),
+            TIMESTAMP, TIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestamp),
+            TIMESTAMP, DATETIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestamp),
+            TIMESTAMP, TIMESTAMP),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, STRING, STRING),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, STRING, DATE),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, STRING, TIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, STRING, DATETIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, STRING, TIMESTAMP),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, DATE, STRING),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, DATE, DATE),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, DATE, TIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, DATE, DATETIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, DATE, TIMESTAMP),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, TIME, STRING),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, TIME, DATE),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, TIME, TIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, TIME, DATETIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, TIME, TIMESTAMP),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, DATETIME, STRING),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, DATETIME, DATE),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, DATETIME, TIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
             TIMESTAMP, DATETIME, DATETIME),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
             TIMESTAMP, DATETIME, TIMESTAMP),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIMESTAMP, STRING),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIMESTAMP, DATE),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx), TIMESTAMP, TIMESTAMP, TIME),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, TIMESTAMP, STRING),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, TIMESTAMP, DATE),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
+            TIMESTAMP, TIMESTAMP, TIME),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
             TIMESTAMP, TIMESTAMP, DATETIME),
-        impl(nullMissingHandling(DateTimeFunction::exprTimestampEx),
+        implWithProperties(nullMissingHandlingWithProperties(DateTimeFunction::exprTimestampEx),
             TIMESTAMP, TIMESTAMP, TIMESTAMP));
   }
 
@@ -740,36 +799,36 @@ private ExprValue exprAddDateDays(ExprValue date, ExprValue days) {
   /**
    * Adds or subtracts time to/from date and returns the result.
    *
-   * @param date A Date/Time/Datetime/Timestamp value to change.
-   * @param time A Date/Time/Datetime/Timestamp object to add/subtract time from.
-   * @param add A flag: true to add, false to subtract.
+   * @param functionProperties A FunctionProperties object.
+   * @param temporal A Date/Time/Datetime/Timestamp value to change.
+   * @param temporalDelta A Date/Time/Datetime/Timestamp object to add/subtract time from.
+   * @param isAdd A flag: true to add, false to subtract.
    * @return A value calculated.
    */
-  private ExprValue exprApplyTime(ExprValue date, ExprValue time, Boolean add) {
-    var timeToAdd = time.type() == TIME
-        ? time.timeValue()
-        : time.datetimeValue().toLocalTime();
-    var dt = date.type() == TIME
-        ? LocalDate.now().atTime(date.timeValue())
-        : date.datetimeValue();
-    var interval = Duration.between(LocalTime.MIN, timeToAdd);
-    dt = add ? dt.plus(interval) : dt.minus(interval);
-    return date.type() == TIME
-        ? new ExprTimeValue(dt.toLocalTime())
-        : new ExprDatetimeValue(dt);
+  private ExprValue exprApplyTime(FunctionProperties functionProperties,
+                                  ExprValue temporal, ExprValue temporalDelta, Boolean isAdd) {
+    var interval = Duration.between(LocalTime.MIN, temporalDelta.timeValue());
+    var result = isAdd
+        ? extractDateTime(temporal, functionProperties).plus(interval)
+        : extractDateTime(temporal, functionProperties).minus(interval);
+    return temporal.type() == TIME
+        ? new ExprTimeValue(result.toLocalTime())
+        : new ExprDatetimeValue(result);
   }
 
   /**
    * Adds time to date and returns the result.
    *
-   * @param date A Date/Time/Datetime/Timestamp value to change.
-   * @param time A Date/Time/Datetime/Timestamp object to add time from.
+   * @param functionProperties A FunctionProperties object.
+   * @param temporal A Date/Time/Datetime/Timestamp value to change.
+   * @param temporalDelta A Date/Time/Datetime/Timestamp object to add time from.
    * @return A value calculated.
    */
-  private ExprValue exprAddTime(ExprValue date, ExprValue time) {
-    return exprApplyTime(date, time, true);
+  private ExprValue exprAddTime(FunctionProperties functionProperties,
+                                ExprValue temporal, ExprValue temporalDelta) {
+    return exprApplyTime(functionProperties, temporal, temporalDelta, true);
   }
-
+  
   /**
    * CONVERT_TZ function implementation for ExprValue.
    * Returns null for time zones outside of +13:00 and -12:00.
@@ -1157,12 +1216,13 @@ private ExprValue exprSubDateInterval(ExprValue date, ExprValue expr) {
   /**
    * Subtracts expr2 from expr1 and returns the result.
    *
-   * @param date A Date/Time/Datetime/Timestamp value to change.
-   * @param time A Date/Time/Datetime/Timestamp to subtract time from.
+   * @param temporal A Date/Time/Datetime/Timestamp value to change.
+   * @param temporalDelta A Date/Time/Datetime/Timestamp to subtract time from.
    * @return A value calculated.
    */
-  private ExprValue exprSubTime(ExprValue date, ExprValue time) {
-    return exprApplyTime(date, time, false);
+  private ExprValue exprSubTime(FunctionProperties functionProperties,
+                                ExprValue temporal, ExprValue temporalDelta) {
+    return exprApplyTime(functionProperties, temporal, temporalDelta, false);
   }
 
   /**
@@ -1185,11 +1245,11 @@ private ExprValue exprTime(ExprValue exprValue) {
    * @param exprValue ExprValue of Timestamp.
    * @return ExprValue.
    */
-  private ExprValue exprTimestamp(ExprValue exprValue) {
+  private ExprValue exprTimestamp(FunctionProperties functionProperties, ExprValue exprValue) {
     if (exprValue instanceof ExprStringValue) {
       return new ExprTimestampValue(exprValue.stringValue());
     }
-    return new ExprTimestampValue(exprValue.timestampValue());
+    return new ExprTimestampValue(DateTimeUtils.extractTimestamp(exprValue, functionProperties));
   }
 
   /**
@@ -1200,8 +1260,11 @@ private ExprValue exprTimestamp(ExprValue exprValue) {
    * @param exprValue2 ExprValue of Timestamp type or String type.
    * @return ExprValue.
    */
-  private ExprValue exprTimestampEx(ExprValue exprValue1, ExprValue exprValue2) {
-    return exprAddTime(exprTimestamp(exprValue1), exprTimestamp(exprValue2));
+  private ExprValue exprTimestampEx(FunctionProperties functionProperties,
+                                    ExprValue exprValue1, ExprValue exprValue2) {
+    return exprAddTime(functionProperties,
+        exprTimestamp(functionProperties, exprValue1),
+        exprTimestamp(functionProperties, exprValue2));
   }
 
   /**
diff --git a/core/src/main/java/org/opensearch/sql/utils/DateTimeUtils.java b/core/src/main/java/org/opensearch/sql/utils/DateTimeUtils.java
index 6ca9486de61..0f8a81fd372 100644
--- a/core/src/main/java/org/opensearch/sql/utils/DateTimeUtils.java
+++ b/core/src/main/java/org/opensearch/sql/utils/DateTimeUtils.java
@@ -139,4 +139,15 @@ public static LocalDateTime extractDateTime(ExprValue value,
         ? ((ExprTimeValue) value).datetimeValue(functionProperties)
         : value.datetimeValue();
   }
+
+  /**
+   * Extracts Instant from a datetime ExprValue.
+   * Uses `FunctionProperties` for `ExprTimeValue`.
+   */
+  public static Instant extractTimestamp(ExprValue value,
+                                         FunctionProperties functionProperties) {
+    return value instanceof ExprTimeValue
+        ? ((ExprTimeValue) value).timestampValue(functionProperties)
+        : value.timestampValue();
+  }
 }
diff --git a/core/src/test/java/org/opensearch/sql/expression/datetime/TimestampTest.java b/core/src/test/java/org/opensearch/sql/expression/datetime/TimestampTest.java
index ad61ebd9956..98c4332b17c 100644
--- a/core/src/test/java/org/opensearch/sql/expression/datetime/TimestampTest.java
+++ b/core/src/test/java/org/opensearch/sql/expression/datetime/TimestampTest.java
@@ -15,38 +15,28 @@
 import java.time.LocalTime;
 import java.util.stream.Stream;
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.extension.ExtendWith;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.CsvSource;
 import org.junit.jupiter.params.provider.MethodSource;
-import org.mockito.Mock;
-import org.mockito.junit.jupiter.MockitoExtension;
 import org.opensearch.sql.data.model.ExprTimestampValue;
-import org.opensearch.sql.data.model.ExprValue;
 import org.opensearch.sql.data.model.ExprValueUtils;
 import org.opensearch.sql.exception.SemanticCheckException;
 import org.opensearch.sql.expression.DSL;
-import org.opensearch.sql.expression.Expression;
 import org.opensearch.sql.expression.ExpressionTestBase;
-import org.opensearch.sql.expression.env.Environment;
 
-@ExtendWith(MockitoExtension.class)
 public class TimestampTest extends ExpressionTestBase {
 
-  @Mock
-  Environment<Expression, ExprValue> env;
-
   @Test
   public void timestamp_one_arg_string() {
-    var expr = dsl.timestamp(DSL.literal("1961-04-12 09:07:00"));
+    var expr = DSL.timestamp(functionProperties, DSL.literal("1961-04-12 09:07:00"));
     assertEquals(TIMESTAMP, expr.type());
-    assertEquals(new ExprTimestampValue("1961-04-12 09:07:00"), expr.valueOf(env));
+    assertEquals(new ExprTimestampValue("1961-04-12 09:07:00"), expr.valueOf());
 
-    expr = dsl.timestamp(DSL.literal("1961-04-12 09:07:00.123456"));
+    expr = DSL.timestamp(functionProperties, DSL.literal("1961-04-12 09:07:00.123456"));
     assertEquals(TIMESTAMP, expr.type());
     assertEquals(LocalDateTime.of(1961, 4, 12, 9, 7, 0, 123456000),
-        expr.valueOf(env).datetimeValue());
+        expr.valueOf().datetimeValue());
   }
 
   /**
@@ -63,42 +53,43 @@ public void timestamp_one_arg_string() {
   public void timestamp_one_arg_string_invalid_format(String value, String testName) {
     // exception thrown from ExprTimestampValue(String) CTOR
     var exception = assertThrows(SemanticCheckException.class,
-        () -> dsl.timestamp(DSL.literal(value)).valueOf(env));
+        () -> DSL.timestamp(functionProperties, DSL.literal(value)).valueOf());
     assertEquals(String.format("timestamp:%s in unsupported format, please "
         + "use yyyy-MM-dd HH:mm:ss[.SSSSSSSSS]", value), exception.getMessage());
   }
 
   @Test
   public void timestamp_one_arg_time() {
-    var expr = dsl.timestamp(dsl.time(DSL.literal("22:33:44")));
+    var expr = DSL.timestamp(functionProperties, DSL.time(DSL.literal("22:33:44")));
     assertEquals(TIMESTAMP, expr.type());
     var refValue = LocalDate.now().atTime(LocalTime.of(22, 33, 44))
         .atZone(ExprTimestampValue.ZONE).toInstant();
-    assertEquals(new ExprTimestampValue(refValue), expr.valueOf(env));
+    assertEquals(new ExprTimestampValue(refValue), expr.valueOf());
   }
 
   @Test
   public void timestamp_one_arg_date() {
-    var expr = dsl.timestamp(dsl.date(DSL.literal("2077-12-15")));
+    var expr = DSL.timestamp(functionProperties, DSL.date(DSL.literal("2077-12-15")));
     assertEquals(TIMESTAMP, expr.type());
     var refValue = LocalDate.of(2077, 12, 15).atStartOfDay()
         .atZone(ExprTimestampValue.ZONE).toInstant();
-    assertEquals(new ExprTimestampValue(refValue), expr.valueOf(env));
+    assertEquals(new ExprTimestampValue(refValue), expr.valueOf());
   }
 
   @Test
   public void timestamp_one_arg_datetime() {
-    var expr = dsl.timestamp(dsl.datetime(DSL.literal("1961-04-12 09:07:00")));
+    var expr = DSL.timestamp(functionProperties, DSL.datetime(DSL.literal("1961-04-12 09:07:00")));
     assertEquals(TIMESTAMP, expr.type());
-    assertEquals(LocalDateTime.of(1961, 4, 12, 9, 7, 0), expr.valueOf(env).datetimeValue());
+    assertEquals(LocalDateTime.of(1961, 4, 12, 9, 7, 0), expr.valueOf().datetimeValue());
   }
 
   @Test
   public void timestamp_one_arg_timestamp() {
     var refValue = new ExprTimestampValue(Instant.ofEpochSecond(10050042));
-    var expr = dsl.timestamp(dsl.timestamp(DSL.literal(refValue)));
+    var expr = DSL.timestamp(functionProperties,
+        DSL.timestamp(functionProperties, DSL.literal(refValue)));
     assertEquals(TIMESTAMP, expr.type());
-    assertEquals(refValue, expr.valueOf(env));
+    assertEquals(refValue, expr.valueOf());
   }
 
   private static Instant dateTime2Instant(LocalDateTime dt) {
@@ -186,10 +177,10 @@ private static Stream<Arguments> getTestData() {
   @ParameterizedTest
   @MethodSource("getTestData")
   public void timestamp_with_two_args(Object arg1, Object arg2, ExprTimestampValue expected) {
-    var expr = dsl.timestamp(
+    var expr = DSL.timestamp(functionProperties,
         DSL.literal(ExprValueUtils.fromObjectValue(arg1)),
         DSL.literal(ExprValueUtils.fromObjectValue(arg2)));
     assertEquals(TIMESTAMP, expr.type());
-    assertEquals(expected, expr.valueOf(env));
+    assertEquals(expected, expr.valueOf());
   }
 }
diff --git a/docs/user/dql/functions.rst b/docs/user/dql/functions.rst
index f094fba48d5..bbc3794557f 100644
--- a/docs/user/dql/functions.rst
+++ b/docs/user/dql/functions.rst
@@ -893,7 +893,7 @@ Antonyms: `SUBTIME`_
 
 Example::
 
-    os> SELECT ADDTIME(TIME('23:59:59'), DATE('2004-01-01')) AS `'23:59:59' + 0`
+    os> SELECT ADDTIME(DATE('2008-12-12'), DATE('2008-11-15')) AS `'2008-12-12' + 0 `
     fetched rows / total rows = 1/1
     +---------------------+
     | '2008-12-12' + 0    |
@@ -2081,11 +2081,38 @@ Example::
 
     os> SELECT SUBTIME(TIMESTAMP('2007-03-01 10:20:30'), DATETIME('2002-03-04 20:40:50')) AS `'2007-03-01 10:20:30' - '20:40:50'`
     fetched rows / total rows = 1/1
-    +-----------------------------------------+
-    | `'2007-03-01 10:20:30' - '20:40:50'`    |
-    |-----------------------------------------|
-    | 2007-02-28 13:39:40                     |
-    +-----------------------------------------+
+    +--------------------------------------+
+    | '2007-03-01 10:20:30' - '20:40:50'   |
+    |--------------------------------------|
+    | 2007-02-28 13:39:40                  |
+    +--------------------------------------+
+
+
+SYSDATE
+-------
+
+Description
+>>>>>>>>>>>
+
+Returns the current date and time as a value in 'YYYY-MM-DD hh:mm:ss[.nnnnnn]'.
+SYSDATE() returns the time at which it executes. This differs from the behavior for `NOW() <#now>`_, which returns a constant time that indicates the time at which the statement began to execute.
+If the argument is given, it specifies a fractional seconds precision from 0 to 6, the return value includes a fractional seconds part of that many digits.
+
+Optional argument type: INTEGER
+
+Return type: DATETIME
+
+Specification: SYSDATE([INTEGER]) -> DATETIME
+
+Example::
+
+    > SELECT SYSDATE() as value_1, SYSDATE(6) as value_2;
+    fetched rows / total rows = 1/1
+    +---------------------+----------------------------+
+    | value_1             | value_2                    |
+    |---------------------+----------------------------|
+    | 2022-08-02 15:39:05 | 2022-08-02 15:39:05.123456 |
+    +---------------------+----------------------------+
 
 
 TIME
diff --git a/docs/user/ppl/functions/datetime.rst b/docs/user/ppl/functions/datetime.rst
index a66e8c4efbb..7a4875c20cb 100644
--- a/docs/user/ppl/functions/datetime.rst
+++ b/docs/user/ppl/functions/datetime.rst
@@ -67,7 +67,7 @@ Example::
     | 2008-12-12 00:00:00 |
     +---------------------+
 
-    os> source=people | `'23:59:59' + 0` = ADDTIME(TIME('23:59:59'), DATE('2004-01-01')) | fields `'23:59:59' + 0`
+    os> source=people | eval `'23:59:59' + 0` = ADDTIME(TIME('23:59:59'), DATE('2004-01-01')) | fields `'23:59:59' + 0`
     fetched rows / total rows = 1/1
     +------------------+
     | '23:59:59' + 0   |
@@ -234,6 +234,111 @@ Example::
     +-------------------------------------------------------+
 
 
+CURDATE
+-------
+
+Description
+>>>>>>>>>>>
+
+Returns the current time as a value in 'YYYY-MM-DD'.
+CURDATE() returns the time at which it executes as `SYSDATE() <#sysdate>`_ does.
+
+Return type: DATE
+
+Specification: CURDATE() -> DATE
+
+Example::
+
+    > source=people | eval `CURDATE()` = CURDATE() | fields `CURDATE()`
+    fetched rows / total rows = 1/1
+    +-------------+
+    | CURDATE()   |
+    |-------------|
+    | 2022-08-02  |
+    +-------------+
+
+
+CURRENT_DATE
+------------
+
+Description
+>>>>>>>>>>>
+
+`CURRENT_DATE()` are synonyms for `CURDATE() <#curdate>`_.
+
+Example::
+
+    > source=people | eval `CURRENT_DATE()` = CURRENT_DATE() | fields `CURRENT_DATE()`
+    fetched rows / total rows = 1/1
+    +------------------+
+    | CURRENT_DATE()   |
+    |------------------+
+    | 2022-08-02       |
+    +------------------+
+
+
+CURRENT_TIME
+------------
+
+Description
+>>>>>>>>>>>
+
+`CURRENT_TIME()` are synonyms for `CURTIME() <#curtime>`_.
+
+Example::
+
+    > source=people | eval `CURRENT_TIME()` = CURRENT_TIME() | fields `CURRENT_TIME()`
+    fetched rows / total rows = 1/1
+    +------------------+
+    | CURRENT_TIME()   |
+    |------------------+
+    | 15:39:05         |
+    +------------------+
+
+
+CURRENT_TIMESTAMP
+-----------------
+
+Description
+>>>>>>>>>>>
+
+`CURRENT_TIMESTAMP()` are synonyms for `NOW() <#now>`_.
+
+Example::
+
+    > source=people | eval `CURRENT_TIMESTAMP()` = CURRENT_TIMESTAMP() | fields `CURRENT_TIMESTAMP()`
+    fetched rows / total rows = 1/1
+    +-----------------------+
+    | CURRENT_TIMESTAMP()   |
+    |-----------------------+
+    | 2022-08-02 15:54:19   |
+    +-----------------------+
+
+
+CURTIME
+-------
+
+Description
+>>>>>>>>>>>
+
+Returns the current time as a value in 'hh:mm:ss'.
+CURTIME() returns the time at which the statement began to execute as `NOW() <#now>`_ does.
+
+Return type: TIME
+
+Specification: CURTIME() -> TIME
+
+Example::
+
+    > source=people | eval `value_1` = CURTIME(), `value_2` = CURTIME() | fields `value_1`, `value_2`
+    fetched rows / total rows = 1/1
+    +-----------+-----------+
+    | value_1   | value_2   |
+    |-----------+-----------|
+    | 15:39:05  | 15:39:05  |
+    +-----------+-----------+
+
+
 DATE
 ----
 
@@ -1092,11 +1197,38 @@ Example::
 
     os> source=people | eval `'2007-03-01 10:20:30' - '20:40:50'` = SUBTIME(TIMESTAMP('2007-03-01 10:20:30'), DATETIME('2002-03-04 20:40:50')) | fields `'2007-03-01 10:20:30' - '20:40:50'`
     fetched rows / total rows = 1/1
-    +-----------------------------------------+
-    | `'2007-03-01 10:20:30' - '20:40:50'`    |
-    |-----------------------------------------|
-    | 2007-02-28 13:39:40                     |
-    +-----------------------------------------+
+    +--------------------------------------+
+    | '2007-03-01 10:20:30' - '20:40:50'   |
+    |--------------------------------------|
+    | 2007-02-28 13:39:40                  |
+    +--------------------------------------+
+
+
+SYSDATE
+-------
+
+Description
+>>>>>>>>>>>
+
+Returns the current date and time as a value in 'YYYY-MM-DD hh:mm:ss[.nnnnnn]'.
+SYSDATE() returns the time at which it executes. This differs from the behavior for `NOW() <#now>`_, which returns a constant time that indicates the time at which the statement began to execute.
+If the argument is given, it specifies a fractional seconds precision from 0 to 6, the return value includes a fractional seconds part of that many digits.
+
+Optional argument type: INTEGER
+
+Return type: DATETIME
+
+Specification: SYSDATE([INTEGER]) -> DATETIME
+
+Example::
+
+    > source=people | eval `value_1` = SYSDATE(), `value_2` = SYSDATE(6) | fields `value_1`, `value_2`
+    fetched rows / total rows = 1/1
+    +---------------------+----------------------------+
+    | value_1             | value_2                    |
+    |---------------------+----------------------------|
+    | 2022-08-02 15:39:05 | 2022-08-02 15:39:05.123456 |
+    +---------------------+----------------------------+
 
 
 TIME

From 95ee90d664c51b7cdd827dadf4b764c43ea8bd5f Mon Sep 17 00:00:00 2001
From: Yury-Fridlyand <yury.fridlyand@improving.com>
Date: Mon, 12 Dec 2022 19:34:13 -0800
Subject: [PATCH 13/14] Typo fix.

Signed-off-by: Yury-Fridlyand <yury.fridlyand@improving.com>
---
 .../opensearch/sql/expression/datetime/DateTimeFunction.java    | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java b/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
index f0d1f208810..a2edbf03581 100644
--- a/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
+++ b/core/src/main/java/org/opensearch/sql/expression/datetime/DateTimeFunction.java
@@ -828,7 +828,7 @@ private ExprValue exprAddTime(FunctionProperties functionProperties,
                                 ExprValue temporal, ExprValue temporalDelta) {
     return exprApplyTime(functionProperties, temporal, temporalDelta, true);
   }
-  
+
   /**
    * CONVERT_TZ function implementation for ExprValue.
    * Returns null for time zones outside of +13:00 and -12:00.

From f938ea83796cefe60b15787cea67999798b2421c Mon Sep 17 00:00:00 2001
From: Yury-Fridlyand <yury.fridlyand@improving.com>
Date: Thu, 15 Dec 2022 12:21:04 -0800
Subject: [PATCH 14/14] Apply suggestions from code review

Signed-off-by: Yury-Fridlyand <yury.fridlyand@improving.com>

Co-authored-by: Andrew Carbonetto <andrewc@bitquilltech.com>
---
 docs/user/dql/functions.rst          | 2 +-
 docs/user/ppl/functions/datetime.rst | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/docs/user/dql/functions.rst b/docs/user/dql/functions.rst
index bbc3794557f..9144ec420bf 100644
--- a/docs/user/dql/functions.rst
+++ b/docs/user/dql/functions.rst
@@ -2167,7 +2167,7 @@ TIMESTAMP
 Description
 >>>>>>>>>>>
 
-Usage: timestamp(expr) constructs a timestamp type with the input string `expr` as an timestamp. If the argument is not a string, it casts `expr` to timestamp type with default timezone UTC. If argument is a time, it applied to today's date before cast.
+Usage: timestamp(expr) constructs a timestamp type with the input string `expr` as an timestamp. If the argument is not a string, it casts `expr` to timestamp type with default timezone UTC. If argument is a time, it applies today's date before cast.
 With two arguments `timestamp(expr1, expr2)` adds the time expression `expr2` to the date or datetime expression `expr1` and returns the result as a timestamp value.
 
 Argument type: STRING/DATE/TIME/DATETIME/TIMESTAMP
diff --git a/docs/user/ppl/functions/datetime.rst b/docs/user/ppl/functions/datetime.rst
index 7a4875c20cb..cef46cd1844 100644
--- a/docs/user/ppl/functions/datetime.rst
+++ b/docs/user/ppl/functions/datetime.rst
@@ -1307,7 +1307,7 @@ TIMESTAMP
 Description
 >>>>>>>>>>>
 
-Usage: timestamp(expr) constructs a timestamp type with the input string `expr` as an timestamp. If the argument is not a string, it casts `expr` to timestamp type with default timezone UTC. If argument is a time, it applied to today's date before cast.
+Usage: timestamp(expr) constructs a timestamp type with the input string `expr` as an timestamp. If the argument is not a string, it casts `expr` to timestamp type with default timezone UTC. If argument is a time, it applies today's date before cast.
 With two arguments `timestamp(expr1, expr2)` adds the time expression `expr2` to the date or datetime expression `expr1` and returns the result as a timestamp value.
 
 Argument type: STRING/DATE/TIME/DATETIME/TIMESTAMP