code: public static function findExpiredSubscriptions(array $arrOptions=array())
  	{
  		$t = static::$strTable;
  		$objDatabase = Database::getInstance();
  
  		$objResult = $objDatabase->prepare("SELECT * FROM $t WHERE active='' AND EXISTS (SELECT * FROM tl_opt_in_related r LEFT JOIN tl_opt_in o ON r.pid=o.id WHERE r.relTable='$t' AND r.relId=$t.id AND o.createdOn<=? AND o.confirmedOn=0)")
  								 ->execute(strtotime('-24 hours'));
  
  		if ($objResult->numRows < 1)
  		{
  			return null;
  		}
  
  		return static::createCollectionFromDbResult($objResult, $t);
  	}
docs: Find subscriptions that have not been activated for more than 24 hours
  
  @param array $arrOptions An optional options array
  
  @return Collection|CommentsNotifyModel[]|CommentsNotifyModel|null A collection of models or null if there are no expired subscriptions