What are the characteristics of China's ancient calendar, the Dayan Calendar?

The Dayan Calendar is a calendar of the Tang Dynasty, which was compiled by the monk Yixing of the Tang Dynasty. It inherited the advantages and strengths of China's ancient astronomy and made corrections to the deficiencies and shortcomings, and thus achieved great success. It had a great influence on the compilation of calendars in later generations.

The most outstanding performance of the Dayan Calendar is that it correctly grasps the speed of the sun's movement on the ecliptic and the law of change. A row of unequal spacing of the second interpolation method is used to deduce that between every two periods, the difference in the ecliptic is the same, but the time distance is different.

The "Dayan Calendar" also pioneered the calculation method of the sundial leakage of nine services and the eclipse difference of nine services.

The Dayan Calendar contains one line of the world's earliest table of tangent functions.

The Dayan Calendar was a relatively advanced calendar in the world at that time. Japan had sent a foreign student, Yoshibe Zenbi, to study astronomy in China, and when he returned home, he took with him one volume of the Dayan Calendar Scriptures and 12 volumes of the Dayan Calendar Main Sengoku. Thus, the Dayan Calendar was widely circulated in Japan, and its influence was great.