How to calculate the chronology of heavenly stems and earthly branches?

Heavenly stems and earthly branches chronology algorithm is as follows:

The formula of heavenly stems and earthly branches chronology is as follows: the number of years minus three, the remainder divided by 10 is the heavenly stems, the cardinal number divided by 12, and the remainder is the earthly branch years. Take 202 1 year as an example, the base of subtracting 3 in this year is 20 18, divide it by 10 to get the remainder of 8, search the sky stem order, and then divide the base of 20 18 by 12 to get the remainder of 2, and recover the ugly branch order.

China used the chronology of cadres and branches in ancient times, and the nouns mentioned in modern history, such as the Sino-Japanese War, the Reform Movement of 1898, and the Revolution of 1911, are all chronologies of cadres and branches. The so-called trunk branch is the abbreviation of ten-day stem and twelve-day branch Heavenly stems and earthly branches is in accordance with certain laws (Yang trunk with Yang branch, Yin trunk with Yin branch. Or single pair, double pair) can be made into 60 pairs, that is, a nail (60 years), and the time is repeatedly recorded.

Tiangan: Ten Tiangan include A, B, C, D, E, F, G, Xin, nonyl and decyl, in which A, C, E, G and nonyl are yang-dried, while B, D, F, Xin and decyl are yin.

Earthly branches: Twelve earthly branches include Zi, Ugly, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu and Hai, among which Zi, Yin, Chen, Wu, Shen and Xu are Yang branches, and Ugly, Mao, Si, Wei, You and Hai are Yang branches. The formula of heavenly stems and earthly branches chronology is: "The number of AD years is reduced by three, divided by 10, the remainder is heavenly stems, the radix is divided by 12, and the remainder is earthly years."

Take 202 1 year as an example. If you subtract 3 from the year, the radix is 20 18. If you divide by 10, the remainder is 8. Inspection sequence (A, B, C, D, E, G, Xin, Ren and Gui). Get "Xin", then divide the radix 20 18 by 12 to get the remainder of 2, and recover the "Ugliness" in the branch order (Zi, Ugly, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu, Hai). So 202 1 is an ugly year (if you get 0, it can be understood as 1, that is, 12).