Like DateOnly(), but will accept a variant that may be Null, a Date or a String.
The variant date/time
Set this time of day as a default
DateOnly(#1 Jan 1985 2:35pm#) => #1 Jan 1985 0:00#
DateOnly(Null) => Null
DateOnly("1 Jan 1985 2:35pm") => #1 Jan 1985 0:00#