DateTime() Date() Time() are deprecated.

Will be `now` in future release.

NEWS.md

@@ -970,6 +970,10 @@ Deprecated or removed
 
   * `Base.@gc_preserve` has been deprecated in favor of `GC.@preserve` ([#25616]).
 
+  * `DateTime()`, `Date()`, and `Time()` have been deprecated, instead use `DateTime(1)`, `Date(1)`
+    and `Time(0)` respectively. In a future release `DateTime()`, `Date()`, and `Time()` will be
+    alternatives to `now()` ([#23724]).
+
 Command-line option changes
 ---------------------------
 

stdlib/Dates/src/deprecated.jl

@@ -41,3 +41,7 @@ import Base.range
 @deprecate range(start::DateTime, len::Integer)  range(start, Day(1), len) false
 @deprecate range(start::Date, len::Integer)      range(start, Day(1), len) false
 
+# PR #23724
+@deprecate DateTime() DateTime(1)
+@deprecate Date() Date(1)
+@deprecate Time() Time(0)

stdlib/Dates/src/types.jl

@@ -314,6 +314,13 @@ DateTime(y, m=1, d=1, h=0, mi=0, s=0, ms=0) = DateTime(Int64(y), Int64(m), Int64
 Date(y, m=1, d=1) = Date(Int64(y), Int64(m), Int64(d))
 Time(h, mi=0, s=0, ms=0, us=0, ns=0) = Time(Int64(h), Int64(mi), Int64(s), Int64(ms), Int64(us), Int64(ns))
 
+# Empty constructors default to 'now'
+if VERSION >= v"0.8-"
+    DateTime() = now()
+    Date() = today()
+    Time() = Time(now())
+end
+
 # Traits, Equality
 Base.isfinite(::Union{Type{T}, T}) where {T<:TimeType} = true
 calendar(dt::DateTime) = ISOCalendar

stdlib/Dates/test/types.jl

@@ -110,6 +110,16 @@ end
     @test Dates.Time(Dates.Hour(4), Dates.Second(10), Dates.Millisecond(15),
                      Dates.Microsecond(20), Dates.Nanosecond(25)) == Dates.Time(4, 0, 10, 15, 20, 25)
 end
+
+@testset "empty constructors" begin
+    if VERSION >= v"0.8-"
+        present = now()
+        @test Dates.DateTime(present) <= Dates.DateTime()
+        @test Dates.Date(present) <= Dates.Date()
+        @test Dates.Time(present) <= Dates.Time()
+    end
+end
+
 @testset "various input types for Date/DateTime" begin
     test = Dates.Date(1, 1, 1)
     @test Dates.Date(Int8(1), Int8(1), Int8(1)) == test