Shoushi Calendar，the most outstanding calendar in ancient China，was compiled by Guo Shoujing，a prominent scientist in the Yuan Dynasty，and his colleagues. Enforced in 1281,throughout the Ming Dynasty and the begin-nin4 of the Qinq Dynasty，the calendar was used for over 360 years.
《授时历》是中国古代最优秀的历法。由元代著名科学家郭守敬等人编制，从1281年开始实行，历经整个明代，一直到清初，共用了360多年。
The reason why the calendar was used for such a long time has much to do with its accuracy in calculation. In the first place，it employed astronomical docu-ments of the highest accuracy in its time. For instance，it set the tropical year at 365.2425 days，which was the exactly the same as that in the currently used Gre-gorian Calendar, 301 years preceding the latter though. Secondly, based on earlier scholars' finding that the length of the tropical year was gradually shortening，the Shoushi Calendar held that the tropical year shortened by 0. 0001 day every 100 years，which was more accurate as compared with earlier researches.
