title: datepicker posts now() even if empty ZF2 Doctrine2
body: <p>I have a form with two dates where I use bootstrap3 datepicker. The dates are not mandatory. When I submit the form and one or both of the dates are not filled out, the posted entity contains the actual datetime instead of beeing NULL. When I check the $_POST the dates are NULL.
  I use doctrine2 and ZF2. Maybe you need more informations... Thanks in advance for any help.</p>