code: public static function adjust($hour, $ampm) {
          $hour = (int)$hour;
          $ampm = strtolower($ampm);
  
          switch ($ampm) {
              case 'am':
                  if ($hour == 12) {
                      $hour = 0;
                  }
                  break;
              case 'pm':
                  if ($hour < 12) {
                      $hour += 12;
                  }
                  break;
          }
  
          return sprintf('%02d', $hour);
      }
docs: Adjusts a non-24-hour number into a 24-hour number.
  
  $hour = Date::adjust(3, 'pm'); // 15
  
  @param   integer $hour hour to adjust
  @param   string $ampm AM or PM
  @return  string