code: 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);
      }
docs: 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