How to calculate the chronology of trunk and branch (AD chronology is converted into trunk and branch chronology in this way)

In ancient China, heavenly stems and earthly branches often used heavenly stems and earthly branches to mark the year, month, day and time for the convenience of farming. * * * there are ten days to do twelve branches. Among them, the twelve earthly branches correspond to the genus one by one, namely: ten heavenly stems: A, B, C, D, E, Ji, Ke, Xin, Ren and Gui; Twelve earthly branches: Zi, Ugly, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu and Hai. 1. Heavenly stems algorithm: the number of years minus 3 and then divided by 10 (without considering the quotient) is the number of digits corresponding to heavenly stems; 2. Earthbranch algorithm: The number of years minus 3 and then divided by 12 (excluding quotient) is the number of digits corresponding to earthbranch. Let's take the year of 20 10 as an example: heavenly stems algorithm: 20 10-3=2007, 2007/10 = more than 200 years, and 7 corresponds to that the seventh place of heavenly stems is Geng, that is, heavenly stems are Geng; Ground branch algorithm: 20 10-3=2007, 2007/ 12= 167, and the third place of the ground branch is yin, that is, the ground branch is yin. To sum up, 20 10 is the year of Gengyin (Tiger) in heavenly stems and earthly branches. Similarly, the year of 20 19 can be calculated as follows: Tiangan: (2019-3)/10 = 201+6 Dizhi: (2019-3)//kloc-.