Minor Description
The @DropDownDatePicker resets to the previous value if someone manually changes the date to an invalid one, but the user is unaware of any validation issues.
For example, we have an Expiration Date field that is set for 2/28/2007 and a user manually changes it to 2/29/2008. When they submit the form (without focusing on the next field) the form passes validation and the user thinks that the date they entered is fine. However, what ends up happening is the date just reverts back to the previous value and the user is now unaware that the changes they made on that date were incorrect and not saved.