Extended data:

The conversion between the chronology of cadres and branches and the chronology of Gregorian calendar;

Because heavenly stems and earthly branches cycles every 60 years, it is impossible to directly calculate the corresponding year value from the main branch. But we can calculate the corresponding year of 60 years according to the main branch, and then further calculate.

Let X be the corresponding sequence of heavenly stems, and the sequence of A-D is1-10; Y is the corresponding order of earthly branches, and sub-hai is 1- 12 in turn. Then the calculation formula of the corresponding order Z is: z = 6x-5y. If it is negative, you can add 60.

Its calculation is based on congruence equations: z ≡ x (mod 10), z ≡ y (mod 12) and x ≡ y (mod 2), which is obtained by solving z≡36x+25y (mod 60) and further simplifying it.

Many historical events in China's modern history were named after heavenly stems and earthly branches's calendar year, such as the Xinyou coup of 186 1, the Sino-Japanese War of 1894, the Reform Movement of 1898 of190/kloc-0.

References:

Baidu Encyclopedia-heavenly stems and earthly branches