Dates: add constructor DateTime(::Date, ::Time)

stdlib/Dates/src/types.jl

@@ -240,7 +240,7 @@ function DateTime(y::Year, m::Month=Month(1), d::Day=Day(1),
                   h::Hour=Hour(0), mi::Minute=Minute(0),
                   s::Second=Second(0), ms::Millisecond=Millisecond(0))
     return DateTime(value(y), value(m), value(d),
-                        value(h), value(mi), value(s), value(ms))
+                    value(h), value(mi), value(s), value(ms))
 end
 
 Date(y::Year, m::Month=Month(1), d::Day=Day(1)) = Date(value(y), value(m), value(d))
@@ -310,6 +310,26 @@ function Time(period::TimePeriod, periods::TimePeriod...)
     return Time(h, mi, s, ms, us, ns)
 end
 
+# Convenience constructor for DateTime from Date and Time
+"""
+    DateTime(d::Date, t::Time)
+
+Construct a `DateTime` type by `Date` and `Time`.
+
+```jldoctest
+julia> d = Date(2018, 1, 1)
+2018-01-01
+
+julia> t = Time(8, 15, 42)
+08:15:42
+
+julia> DateTime(d, t)
+2018-01-01T08:15:42
+```
+"""
+DateTime(d::Date, t::Time) =
+    DateTime(UTM(value(d) * 86400000 + value(t) / 1000000))
+
 # Fallback constructors
 DateTime(y, m=1, d=1, h=0, mi=0, s=0, ms=0) = DateTime(Int64(y), Int64(m), Int64(d), Int64(h), Int64(mi), Int64(s), Int64(ms))
 Date(y, m=1, d=1) = Date(Int64(y), Int64(m), Int64(d))