SlightPHP\PHPMailer::RFCDate PHP Method

    private static function RFCDate()
    {
        $tz = date('Z');
        $tzs = $tz < 0 ? '-' : '+';
        $tz = abs($tz);
        $tz = (int) ($tz / 3600) * 100 + $tz % 3600 / 60;
        $result = sprintf("%s %s%04d", date('D, j M Y H:i:s'), $tzs, $tz);
        return $result;
    }