--- date_popup/date_popup.module.~1~	2012-08-13 10:22:34.000000000 +0100
+++ date_popup/date_popup.module	2013-07-18 09:31:29.000000000 +0100
@@ -508,7 +508,7 @@ function date_popup_validate($element, &
   }
 
   // If the created date is valid, set it.
-  $value = !empty($date) ? $date->format(DATE_FORMAT_DATETIME) : NULL;
+  $value = !empty($date) ? $date->format($element['#date_format']) : NULL;
   form_set_value($element, $value, $form_state);
 }