public static function dateValue($val)
    {
      //2009-05-13T20:23:43Z
        if (!preg_match('/^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2})Z/', $val, $matches)) {
            throw new PListException("Unknown date format: $val");
        }
        return gmmktime($matches[4], $matches[5], $matches[6], $matches[2], $matches[3], $matches[1]);
    }