([1-9]|1[012])/([1-9]|[12][0-9]|3[01])/0[0-9]$
This will verify if the date is mM/dd/yy, where m is optional. Example: 9/21/07 or 11/21/07
(0[1-9]|1[012])[- /.](0[1-9]|[12][0-9]|3[01])[- /.](19|20)\d\d
This will verify if the date is mm/dd/yyyy. Example: 12/12/2007
