TimeType subtraction using promote (#49700)

Author: baumgold

stdlib/Dates/src/arithmetic.jl

@@ -7,6 +7,7 @@
 # TimeType arithmetic
 (+)(x::TimeType) = x
 (-)(x::T, y::T) where {T<:TimeType} = x.instant - y.instant
+(-)(x::TimeType, y::TimeType) = -(promote(x, y)...)
 
 # Date-Time arithmetic
 """

stdlib/Dates/test/arithmetic.jl

@@ -10,6 +10,13 @@ using Dates
     b = Dates.Time(11, 59, 59)
     @test Dates.CompoundPeriod(a - b) == Dates.Hour(12)
 end
+
+@testset "TimeType arithmetic" begin
+    a = Date(2023, 5, 1)
+    b = DateTime(2023, 5, 2)
+    @test b - a == Day(1)
+end
+
 @testset "Wrapping arithmetic for Months" begin
     # This ends up being trickier than expected because
     # the user might do 2014-01-01 + Month(-14)