src/util/Date.php
public static function dos2unix($timestamp = false) {
        $sec = 2 * ($timestamp & 0x1f);
        $min = ($timestamp >> 5) & 0x3f;
        $hrs = ($timestamp >> 11) & 0x1f;
        $day = ($timestamp >> 16) & 0x1f;
        $mon = ($timestamp >> 21) & 0x0f;
        $year = ($timestamp >> 25) & 0x7f;

        return mktime($hrs, $min, $sec, $mon, $day, $year + 1980);
    }
public static function dos2unix($timestamp = false) {
        $sec = 2 * ($timestamp & 0x1f);
        $min = ($timestamp >> 5) & 0x3f;
        $hrs = ($timestamp >> 11) & 0x1f;
        $day = ($timestamp >> 16) & 0x1f;
        $mon = ($timestamp >> 21) & 0x0f;
        $year = ($timestamp >> 25) & 0x7f;

        return mktime($hrs, $min, $sec, $mon, $day, $year + 1980);
    }
Converts a DOS timestamp to UNIX format.There are very few cases where
this is needed, but some binary formats use it (eg: zip files.)
Converting the other direction is done using {@link Date::unix2dos}.

$unix = Date::dos2unix($dos);

@param   integer $timestamp DOS timestamp
@return  integer