ZF-2003: Zend_Validate_Date to support more formats than YYYY-MM-DD
Zend_Validate_Date currently requires an input format of YYYY-MM-DD, such as 2007-03-17. In the spirit of flexibility, the validation class should accept various other formats. Further, it should make use of Zend_Date, for DRYer code.
Priority minor since it is trivial to preformat a date such that it follows the YYYY-MM-DD format.