怎么计算多少天后的日期

简介：A tall and thin man, who was as tall as a bamboo pole, opened his mouth to reveal two big yellow fangs and two rather wretched little eyes. He wore a bamboo hat on his head. He first stood on tiptoe and looked at Su Can and the others from a distance, and then whispered to them. Du Yi said: Lao Du, we have been in a relationship for many years. You have to explain to me, what are the origins of the big one and the small one?