What is heavenly stems and earthly branches?

Used to arrange year numbers and dates in the summer calendar.

Heavenly stems and earthly branches, referred to as Ganzhi for short, originated from the observation of astronomical phenomena in ancient China.

Ten cadres refer to meeting, understanding, softness, strength, harmony, slaughter, chapter, weight, metaphysics and yang.

Twelve earthly branches refer to people who are trapped in hiding, enthusiastic people, people raised by taking photos, people who are single-handed, people in charge of Xu, people in the wilderness, people who are hiding, people who are in contact with Xie, people on the beach, people who are in trouble, and people in the depths.

The simplified heavenly stems and earthly branches: "A, B, C, D, E, Ji, G, Xin, Man and Ghost" is called the ten heavenly stems, and "Zi, Ugly, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu and Hai" are called the twelve earthly branches.

Ten heavenly stems and twelve earthly branches are matched in turn to form sixty basic units, and they cooperate with each other in a fixed order to form the chronology of the stems and branches. Heavenly stems and earthly branches's invention has far-reaching influence. He still uses heavenly stems and earthly branches in calendar, mathematics, calculation, naming and so on.