Stumbled across this tip the other day:
http://dotnettipoftheday.org/tips/validate-format-of-integer-double-date-currency.aspx
It turns out that you can validate date inputs with a CompareValidator by setting the Operator property to DataTypeCheck and ValidationDataType to Date (or Integer, Double, Currency, etc.).
This was a new one on me, I had always assumed that the CompareValidator was just used for comparing the value of a control with another control (or a constant value) which is what the name (and MSDN) would suggest. I don't know why Microsoft didn't create a separate control called a DataTypeValidator with this functionality rather than hide it within the CompareValidator.
