code: protected function getStartDate()
      {
          $StartDate = false;
          $objStartDate = \Database::getInstance()->prepare("SELECT
                                                             MIN(`tstamp`) AS YMD
                                                             FROM `tl_dlstatdets`
                                                             WHERE 1")
                                                  ->execute();
          if ($objStartDate->YMD !== null)
          {
              $StartDate = $this->parseDate($GLOBALS['TL_CONFIG']['dateFormat'], $objStartDate->YMD);
  
          }
  
          return $StartDate;
      }
docs: Get Startdate of detailed logging
  @return string    Date