public function filter($value)
 {
     if (is_array($value)) {
         $value = vkNgine_Form_Element_Date::getDatestring($value, $this->getDateFormat());
     }
     if ($value == $this->getEmptyDate()) {
         $value = null;
     }
     return $value;
 }
 /**
  * Enter description here ...
  * 
  * @param string $value
  * @param string $format
  * @return Ambigous <string, mixed>
  */
 public function getDateValue($value, $format = 'yyyy-mm-dd')
 {
     return vkNgine_Form_Element_Date::getDatestring($value, $format);
 }