Multiple datepickers on page but require only one to have a vlaue

Multiple datepickers on page but require only one to have a vlaue

I have three datepickers on a form which work fine. But I want only one of them to require a date to be selected.
When the non-required ones are left blank and the form is submitted they return a default date of 30-11-0001. Is it possible to return a null date (blank)?