code: protected function storeLastRun()
      {
          // Silence warnings, which might be caused by multiple possible
          // failures. We handle and log them anyways.
          if ( !@file_put_contents( $this->lockDir . '/lastRun', time() ) )
          {
              $this->logger->log(
                  'Failure storing last run time: ' . ( isset( $php_errormsg ) ? $php_errormsg : 'Unknown error - enable the track_errors ini directive.' ),
                  Logger::ERROR
              );
              return;
          }
  
          $this->logger->log( 'Stored last run time.', Logger::INFO );
      }
docs: Store last run time
  
  Stores the time and date of the last run of the executor.
  
  @return void