public function getDOSTimestamp()
    {
        $time = getdate($this->getTimestamp());

        if ($time['year'] < 1980) {
            $time['year']    = 1980;
            $time['mon']     = 1;
            $time['mday']    = 1;
            $time['hours']   = 0;
            $time['minutes'] = 0;
            $time['seconds'] = 0;
        }

        return (($time['year'] - 1980) << 25)
               | ($time['mon'] << 21)
               | ($time['mday'] << 16)
               | ($time['hours'] << 11)
               | ($time['minutes'] << 5)
               | ($time['seconds'] >> 1);
    }