Horde_Date::setDefaultFormat PHP Method

    public function setDefaultFormat($format)
    {
        $this->_defaultFormat = $format;
    }

 /**
  * @param   string  $string
  * @return  Horde_Date
  */
 public function stringToDate($string)
 {
     if (empty($string) || preg_replace('/[^\\d]/', '', $string) == 0) {
         return null;
     }
     $d = new Horde_Date($string);
     $d->setDefaultFormat('Y-m-d');
     return $d;
 }