Fix: Calculation for occurrences include DST transitions correctly

Ical.Net.Tests/CalendarEventTest.cs

@@ -427,34 +427,37 @@ public void EventResourcesCanBeZeroedOut()
     public void HourMinuteSecondOffsetParsingTest()
     {
         const string ical =
-            @"BEGIN:VCALENDAR
-PRODID:-//1&1 Mail & Media GmbH/GMX Kalender Server 3.10.0//NONSGML//DE
-VERSION:2.0
-CALSCALE:GREGORIAN
-METHOD:REQUEST
-BEGIN:VTIMEZONE
-TZID:Europe/Brussels
-TZURL:http://tzurl.org/zoneinfo/Europe/Brussels
-X-LIC-LOCATION:Europe/Brussels
-BEGIN:DAYLIGHT
-TZOFFSETFROM:-001730
-TZOFFSETTO:-001730
-TZNAME:CEST
-DTSTART:19810329T020000
-RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU
-END:DAYLIGHT
-BEGIN:STANDARD
-TZOFFSETFROM:+001730
-TZOFFSETTO:+001730
-TZNAME:BMT
-DTSTART:18800101T000000
-RDATE:18800101T000000
-END:STANDARD
-END:VTIMEZONE
-END:VCALENDAR";
+            """
+            BEGIN:VCALENDAR
+            PRODID:-//1&1 Mail & Media GmbH/GMX Kalender Server 3.10.0//NONSGML//DE
+            VERSION:2.0
+            CALSCALE:GREGORIAN
+            METHOD:REQUEST
+            BEGIN:VTIMEZONE
+            TZID:Europe/Brussels
+            TZURL:http://tzurl.org/zoneinfo/Europe/Brussels
+            X-LIC-LOCATION:Europe/Brussels
+            BEGIN:DAYLIGHT
+            TZOFFSETFROM:-001730
+            TZOFFSETTO:-001730
+            TZNAME:CEST
+            DTSTART:19810329T020000
+            RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU
+            END:DAYLIGHT
+            BEGIN:STANDARD
+            TZOFFSETFROM:+001730
+            TZOFFSETTO:+001730
+            TZNAME:BMT
+            DTSTART:18800101T000000
+            RDATE:18800101T000000
+            END:STANDARD
+            END:VTIMEZONE
+            END:VCALENDAR
+            """;
         var timezones = Calendar.Load(ical)
             .TimeZones.First()
-            .Children.Cast<CalendarComponent>();
+            .Children.Cast<CalendarComponent>()
+            .ToArray();
 
         var positiveOffset = timezones
             .Skip(1).Take(1).First()
@@ -472,78 +475,99 @@ public void HourMinuteSecondOffsetParsingTest()
 
 
     [Test, Category("CalendarEvent")]
-    public void TestGetEffectiveDuration()
+    public void GetNominalDurationTests()
     {
-        var now = _now.Subtract(TimeSpan.FromTicks(_now.Ticks % TimeSpan.TicksPerSecond));
+        var dt = new DateTime(2025, 3, 1, 14, 30, 0);
+        const string tzIdStart = "America/New_York";
+        const string tzIdEnd = "Europe/London";
 
-        var evt = new CalendarEvent()
+        var evt = new CalendarEvent
         {
-            DtStart = new CalDateTime(DateOnly.FromDateTime(now), TimeOnly.FromDateTime(now)),
-            DtEnd = new CalDateTime(DateOnly.FromDateTime(now.AddHours(1)), TimeOnly.FromDateTime(now.AddHours(1)))
+            DtStart = new CalDateTime(DateOnly.FromDateTime(dt), TimeOnly.FromDateTime(dt), tzIdStart),
+            DtEnd = new CalDateTime(DateOnly.FromDateTime(dt.AddHours(1)), TimeOnly.FromDateTime(dt.AddHours(1)), tzIdEnd)
         };
 
         Assert.Multiple(() =>
         {
-            Assert.That(evt.DtStart.Value, Is.EqualTo(now));
-            Assert.That(evt.DtEnd.Value, Is.EqualTo(now.AddHours(1)));
-            Assert.That(evt.GetFirstDuration(), Is.EqualTo(TimeSpan.FromHours(1)));
+            Assert.That(evt.DtStart.Value, Is.EqualTo(dt));
+            Assert.That(evt.DtEnd.Value, Is.EqualTo(dt.AddHours(1)));
+            Assert.That(evt.GetTimeSpanToAddToPeriodStartTime(), Is.EqualTo(TimeSpan.FromHours(1)));
         });
 
-        evt = new CalendarEvent()
+        evt = new CalendarEvent
         {
-            DtStart = new CalDateTime(DateOnly.FromDateTime(now.Date), TimeOnly.FromDateTime(now.Date)),
-            DtEnd = new CalDateTime(DateOnly.FromDateTime(now.Date.AddHours(1)), TimeOnly.FromDateTime(now.Date.AddHours(1)))
+            DtStart = new CalDateTime(DateOnly.FromDateTime(dt.Date)),
+            DtEnd = new CalDateTime(DateOnly.FromDateTime(dt.Date))
         };
 
         Assert.Multiple(() =>
         {
-            Assert.That(evt.DtStart.Value, Is.EqualTo(now.Date));
-            Assert.That(evt.GetFirstDuration(), Is.EqualTo(TimeSpan.FromHours(1)));
+            Assert.That(evt.DtStart.Value, Is.EqualTo(dt.Date));
+            Assert.That(evt.GetTimeSpanToAddToPeriodStartTime(), Is.EqualTo(TimeSpan.Zero));
         });
 
-        evt = new CalendarEvent()
+        evt = new CalendarEvent
         {
-            DtStart = new CalDateTime(DateOnly.FromDateTime(now)),
+            DtStart = new CalDateTime(DateOnly.FromDateTime(dt)),
         };
 
         Assert.Multiple(() =>
         {
-            Assert.That(evt.DtStart.Value, Is.EqualTo(now.Date));
-            Assert.That(evt.GetFirstDuration(), Is.EqualTo(TimeSpan.FromDays(1)));
+            Assert.That(evt.DtStart.Value, Is.EqualTo(dt.Date));
+            Assert.That(evt.Duration, Is.Null);
+            Assert.That(evt.GetTimeSpanToAddToPeriodStartTime(), Is.EqualTo(TimeSpan.FromDays(1)));
         });
 
-        evt = new CalendarEvent()
+        evt = new CalendarEvent
         {
-            DtStart = new CalDateTime(DateOnly.FromDateTime(now), TimeOnly.FromDateTime(now)),
+            DtStart = new CalDateTime(DateOnly.FromDateTime(dt), TimeOnly.FromDateTime(dt)),
             Duration = TimeSpan.FromHours(2),
         };
 
         Assert.Multiple(() => {
-            Assert.That(evt.DtStart.Value, Is.EqualTo(now));
+            Assert.That(evt.DtStart.Value, Is.EqualTo(dt));
             Assert.That(evt.DtEnd, Is.Null);
-            Assert.That(evt.GetFirstDuration(), Is.EqualTo(TimeSpan.FromHours(2)));
+            Assert.That(evt.GetTimeSpanToAddToPeriodStartTime(), Is.EqualTo(TimeSpan.FromHours(2)));
         });
 
         evt = new CalendarEvent()
         {
-            DtStart = new CalDateTime(DateOnly.FromDateTime(now.Date), TimeOnly.FromDateTime(now.Date)),
+            DtStart = new CalDateTime(DateOnly.FromDateTime(dt.Date), TimeOnly.FromDateTime(dt.Date)),
             Duration = TimeSpan.FromHours(2),
         };
 
         Assert.Multiple(() => {
-            Assert.That(evt.DtStart.Value, Is.EqualTo(now.Date));
-            Assert.That(evt.GetFirstDuration(), Is.EqualTo(TimeSpan.FromHours(2)));
+            Assert.That(evt.DtStart.Value, Is.EqualTo(dt.Date));
+            Assert.That(evt.GetTimeSpanToAddToPeriodStartTime(), Is.EqualTo(TimeSpan.FromHours(2)));
         });
 
         evt = new CalendarEvent()
         {
-            DtStart = new CalDateTime(DateOnly.FromDateTime(now)),
+            DtStart = new CalDateTime(DateOnly.FromDateTime(dt)),
             Duration = TimeSpan.FromDays(1),
         };
 
         Assert.Multiple(() => {
-            Assert.That(evt.DtStart.Value, Is.EqualTo(now.Date));
-            Assert.That(evt.GetFirstDuration(), Is.EqualTo(TimeSpan.FromDays(1)));
+            Assert.That(evt.DtStart.Value, Is.EqualTo(dt.Date));
+            Assert.That(evt.GetTimeSpanToAddToPeriodStartTime(), Is.EqualTo(TimeSpan.FromDays(1)));
+        });
+    }
+
+    [Test]
+    public void EitherEndTime_OrDuraction_CanBeSet()
+    {
+        var evt = new CalendarEvent()
+        {
+            DtStart = new CalDateTime(2025, 10, 11, 12, 13, 14, CalDateTime.UtcTzId)
+        };
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(() => evt.DtEnd = new CalDateTime(2025, 12, 11), Throws.Nothing);
+            Assert.That(() => evt.Duration = TimeSpan.FromDays(1), Throws.InvalidOperationException);
+            Assert.That(() => evt.DtEnd = null, Throws.Nothing);
+            Assert.That(() => evt.Duration = TimeSpan.FromDays(1), Throws.Nothing);
+            Assert.That(() => evt.DtEnd = new CalDateTime(2025, 12, 11), Throws.InvalidOperationException);
         });
     }
 }

Ical.Net.Tests/CollectionHelpersTests.cs

@@ -24,7 +24,6 @@ public void ExDateTests()
     {
         Assert.Multiple(() =>
         {
-            Assert.That(GetExceptionDates(), Is.EqualTo(GetExceptionDates()));
             Assert.That(GetExceptionDates(), Is.Not.Null);
             Assert.That(GetExceptionDates(), Is.Not.EqualTo(null));
         });

Ical.Net.Tests/CopyComponentTests.cs

@@ -60,7 +60,6 @@ public static IEnumerable CopyCalendarTest_TestCases()
     {
         DtStart = new CalDateTime(_now),
         DtEnd = new CalDateTime(_later),
-        Duration = TimeSpan.FromHours(1),
     };
 
     private static string SerializeEvent(CalendarEvent e) => new CalendarSerializer().SerializeToString(new Calendar { Events = { e } });
@@ -199,4 +198,4 @@ public void CopyJournalTest()
             Assert.That(copy.Status, Is.EqualTo(orig.Status));
         });
     }
-}
+}

Ical.Net.Tests/EqualityAndHashingTests.cs

@@ -79,7 +79,6 @@ public void Event_Tests(CalendarEvent incoming, CalendarEvent expected)
     {
         DtStart = new CalDateTime(_nowTime),
         DtEnd = new CalDateTime(_later),
-        Duration = TimeSpan.FromHours(1),
     };
 
     private static string SerializeEvent(CalendarEvent e) => new CalendarSerializer().SerializeToString(new Calendar { Events = { e } });
@@ -112,7 +111,6 @@ public void Calendar_Tests()
         var e = new CalendarEvent
         {
             DtStart = new CalDateTime(_nowTime),
-            DtEnd = new CalDateTime(_later),
             Duration = TimeSpan.FromHours(1),
             RecurrenceRules = new List<RecurrencePattern> { rruleA },
         };
@@ -130,7 +128,6 @@ public void Calendar_Tests()
         expectedCalendar.Events.Add(new CalendarEvent
         {
             DtStart = new CalDateTime(_nowTime),
-            DtEnd = new CalDateTime(_later),
             Duration = TimeSpan.FromHours(1),
             RecurrenceRules = new List<RecurrencePattern> { rruleB },
         });
@@ -501,4 +498,4 @@ public void CalDateTimeComparisonOperatorTests()
         TestComparison((dt1, dt2) => dt1 < dt2, (i1, i2) => i1 < i2);
         TestComparison((dt1, dt2) => dt1 <= dt2, (i1, i2) => i1 <= i2);
     }
-}
+}

Ical.Net.Tests/PeriodTests.cs

@@ -0,0 +1,97 @@
+//
+// Copyright ical.net project maintainers and contributors.
+// Licensed under the MIT license.
+//
+
+#nullable enable
+using System;
+using Ical.Net.DataTypes;
+using NUnit.Framework;
+
+namespace Ical.Net.Tests;
+
+[TestFixture]
+public class PeriodTests
+{
+    [Test]
+    public void CreatePeriodWithArguments()
+    {
+        var period = new Period(new CalDateTime(2025, 1, 1, 0, 0, 0, "America/New_York"));
+        var periodWithEndTime = new Period(new CalDateTime(2025, 1, 1, 0, 0, 0, "America/New_York"), new CalDateTime(2025, 1, 1, 1, 0, 0, "America/New_York"));
+        var periodWithDuration = new Period(new CalDateTime(2025, 1, 1, 0, 0, 0, "America/New_York"), new TimeSpan(1, 0, 0));
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(period.StartTime, Is.EqualTo(new CalDateTime(2025, 1, 1, 0, 0, 0, "America/New_York")));
+            Assert.That(period.EndTime, Is.Null);
+            Assert.That(period.Duration, Is.Null);
+
+            Assert.That(periodWithEndTime.StartTime, Is.EqualTo(new CalDateTime(2025, 1, 1, 0, 0, 0, "America/New_York")));
+            Assert.That(periodWithEndTime.EndTime, Is.EqualTo(new CalDateTime(2025, 1, 1, 1, 0, 0, "America/New_York")));
+            Assert.That(periodWithEndTime.Duration, Is.EqualTo(new TimeSpan(1, 0, 0)));
+
+            Assert.That(periodWithDuration.StartTime, Is.EqualTo(new CalDateTime(2025, 1, 1, 0, 0, 0, "America/New_York")));
+            Assert.That(periodWithDuration.EndTime, Is.EqualTo(new CalDateTime(2025, 1, 1, 1, 0, 0, "America/New_York")));
+            Assert.That(periodWithDuration.Duration, Is.EqualTo(new TimeSpan(1, 0, 0)));
+        });
+    }
+
+    [Test]
+    public void CreatePeriodWithInvalidArgumentsShouldThrow()
+    {
+        Assert.Throws<ArgumentException>(() => _ = new Period(new CalDateTime(2025, 1, 1, 0, 0, 0, "America/New_York"),
+            new CalDateTime(2025, 1, 1, 0, 0, 0, "America/New_York")));
+        Assert.Throws<ArgumentException>(() =>
+            _ = new Period(new CalDateTime(2025, 1, 1, 0, 0, 0, "America/New_York"), new TimeSpan(-1, 0, 0)));
+    }
+    [Test]
+    public void SetAndGetStartTime()
+    {
+        var period = new Period(new CalDateTime(DateTime.UtcNow));
+        var startTime = new CalDateTime(2025, 1, 1, 0, 0, 0);
+        period.StartTime = startTime;
+
+        Assert.That(period.StartTime, Is.EqualTo(startTime));
+    }
+
+    [Test]
+    public void SetEndTime_GetDuration()
+    {
+        var period = new Period(new CalDateTime(2025, 1, 1, 0, 0, 0));
+        var endTime = new CalDateTime(2025, 1, 31, 0, 0, 0);
+        period.EndTime = endTime;
+
+        Assert.That(period.EndTime, Is.EqualTo(endTime));
+        Assert.That(period.GetOriginalValues().EndTime, Is.EqualTo(endTime));
+        Assert.That(period.GetOriginalValues().Duration, Is.Null);
+        Assert.That(period.Duration, Is.EqualTo(new TimeSpan(30, 0, 0, 0)));
+    }
+
+    [Test]
+    public void SetDuration_GetEndTime()
+    {
+        var period = new Period(new CalDateTime(2025, 1, 1, 0, 0, 0));
+        var duration = new TimeSpan(1, 0, 0);
+        period.Duration = duration;
+
+        Assert.That(period.Duration, Is.EqualTo(duration));
+        Assert.That(period.GetOriginalValues().Duration, Is.EqualTo(duration));
+        Assert.That(period.GetOriginalValues().EndTime, Is.Null);
+        Assert.That(period.EndTime, Is.EqualTo(new CalDateTime(2025, 1, 1, 1, 0, 0)));
+    }
+
+    [Test]
+    public void CollidesWithPeriod()
+    {
+        var period1 = new Period(new CalDateTime(2025, 1, 1, 0, 0, 0), new TimeSpan(1, 0, 0));
+        var period2 = new Period(new CalDateTime(2025, 1, 1, 0, 30, 0), new TimeSpan(1, 0, 0));
+        var period3 = new Period(new CalDateTime(2025, 1, 1, 1, 30, 0), new TimeSpan(1, 0, 0));
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(period1.CollidesWith(period2), Is.True);
+            Assert.That(period1.CollidesWith(period3), Is.False);
+            Assert.That(period2.CollidesWith(period3), Is.True);
+        });
+    }
+}