What date type?  DateTime?  A DateTime instance is always a valid date
and time, though it may fall outside of some range you require.

Or do you mean you want to validate a string to verify it represents an
actual date?  You could use DateTime.TryParse() to do that, though of
course there are a wide variety of strings that a human could recognize
as a date but which would fail to be parsed.  Still, using TryParse()
should give you results useful in a computer program.  :)

Pete

What are you looking for ?

A DateTime type is a DateTime type.

Are you looking to test whether a string contains
a valid date according to either standard formats
or a custom format ?

If that is the case try look at DateTime Parse and
ParseExact methods (or TryParse and TryParseExact).

Arne