DELIMITER $$
CREATE OR REPLACE DEFINER=`root`@`localhost` FUNCTION `vn`.`getDueDate`(vDated DATE, vDayToPay INT)
	RETURNS date
	NOT DETERMINISTIC
	NO SQL
BEGIN
	DECLARE vDued DATE;

	IF vDayToPay = 0 THEN
		RETURN vDated;
	END IF;

	SET vDued = TIMESTAMPADD(DAY,vDayToPay MOD 30, LAST_DAY(TIMESTAMPADD(MONTH, vDayToPay DIV 30, vDated)));

	RETURN vDued;
END$$
DELIMITER ;