Horde_Kolab_Format_Date::writeDate PHP Method

    public static function writeDate(DateTime $date)
    {
        return $date->format('Y-m-d');
    }

 /**
  * Update the specified attribute.
  *
  * @param string                        $name        The name of the attribute
  *                                                   to be updated.
  * @param mixed                         $value       The value to store.
  * @param DOMNode                       $parent_node The parent node of the
  *                                                   node that should be
  *                                                   updated.
  * @param Horde_Kolab_Format_Xml_Helper $helper      A XML helper instance.
  * @param array                         $params      The parameters for this
  *                                                   write operation.
  * @param DOMNode|NULL                  $old_node    The previous value (or
  *                                                   null if there is none).
  *
  * @return DOMNode|boolean The new/updated child node or false if this
  *                         failed.
  *
  * @throws Horde_Kolab_Format_Exception If converting the data to XML failed.
  */
 public function saveNodeValue($name, $value, $parent_node, Horde_Kolab_Format_Xml_Helper $helper, $params = array(), $old_node = false)
 {
     if (!isset($value) || !$value instanceof DateTime) {
         throw new Horde_Kolab_Format_Exception(sprintf('Missing or invalid date for the "%s" entry!', $name));
     }
     $date = Horde_Kolab_Format_Date::writeDate($value);
     $node = parent::saveNodeValue($name, $date, $parent_node, $helper, $params, $old_node);
     return $node;
 }