public static function dateTimeFormat()
    {
        return self::pickOne(array(
            DATE_ATOM,
            DATE_COOKIE,
            DATE_ISO8601,
            DATE_RFC822,
            DATE_RFC850,
            DATE_RFC1036,
            DATE_RFC1123,
            DATE_RFC2822,
            DATE_RSS,
            DATE_W3C,
        ));
    }