Because as early as 2697 BC, when the Yellow Emperor, the ancestor of China, founded the country, he was ordered to explore the qi of heaven and earth and the five elements (water, fire and earth in Jin Mu), which opened the ten-day merits of A, B, C, D, E, Ji, G, Xin, Ren and Gui, as well as Zi, Ugly, Yin, Mao, Chen, Si, Wu and Mao.

Ten heavenly stems and twelve earthly branches are matched in turn, and sixty combinations from Jiazi to Guihai and * * * are called Sixty Jiazi.

Extended data:

I. Year of Jiazi

The 1 year of a flower in the trunk calendar of China traditional calendar is called "Jiazi Year".

The calculation formula of Jiazi year corresponding to Gregorian calendar year: Let the year be y, and get x, 60x+4 = y..

For example, x = 33 60 * 33+4 =1980+4 =1984.

1984 is the year of Jiazi.

Another name for 20 or 60 years:

heavenly stems and earthly branches

Ten heavenly stems and twelve earthly branches are matched in turn, and sixty combinations from Jiazi to Guihai and * * * are called Sixty Jiazi.

Heavenly stems and earthly branches:

Tiangan: A, B, C, D, E, Ji, G, Xin, Ren and Gui.

Dizhi: Zi, Ugly, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu and Hai.

Reference: Baidu Encyclopedia-Jiazi