Guo Shoujing improved simple instruments and standard watches. What did he modify?

Summary: Guo Shoujing improved simple instruments and standard tables, presided over nationwide astronomical surveys, and he also presided over the revision of chronicles.

Shoushi Calendar, the calendar name implemented in Yuan Dynasty 128 1 year (eighteen years from Yuan Dynasty to Yuan Dynasty), was named after Kublai Khan of Yuan Shizu, and it was called Shoushi Calendar in original works and history books. This method takes 365.2425 as one year old, which is only 25.92 seconds different from the observed value of 365.2422 in modern times. Its accuracy is equivalent to that of the Gregorian calendar (referring to 1582 Gregorian calendar), but it was adopted more than 300 years earlier than that of the West.

In A.D. 1276 (13th year of Yuan Dynasty), Yuan Shizu ordered Xu Heng to "preside over the affairs of Taishi Museum" and take full charge of this work, with Guo Shoujing and Xun Wang as deputy curators.

Historical significance:

This calendar reflected the new level of astronomical calendar in China at that time. It has many innovations, such as setting the tropical year to 365.2425 days, which is only 25.92 seconds shorter than the actual time for the earth to go around the sun, and is exactly the same as the Gregorian calendar used in the modern world.