private function getBiddingResponse()
 {
     $difference = MediDateTime::differenceUntilNow($this->timer_start);
     if ($difference >= $this->timing_duration) {
         $this->openChecking();
         return self::AUCTION_STATUS_MESSAGE_CHECKING;
     } else {
         return MediDateTime::differenceToTime($this->timing_duration - $difference);
     }
 }