How was ancient heavenly stems and earthly branches divided from time?

Heavenly stems and earthly branches is short for main branch. A, B, C, D, E, Ji, Geng, Xin, Man and Ghost are called ten heavenly stems, while Zi, Ugly, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu and Hai are called twelve earthly branches. The composition of heavenly stems and earthly branches formed the ancient chronology. In folklore, people think that the sky is dry and corresponds to some omens. Ten branches and twelve branches are matched in turn to form sixty basic units, forming a set of branches and disciplines. According to Oracle Bone Inscriptions unearthed from Yin Ruins, heavenly stems and earthly branches was mainly used for recording dates, divination and cooperation among Han people, and later it was more used in the fields of geomantic omen, astrology and so on. The calendar in which the main branch records the year, month and day was called the main branch calendar [1].

Heavenly stems and earthly branches is the abbreviation of "Ganzhi". In Ci Yuan, it is said that the "trunk" is taken from the "trunk" of trees.

Ten-day cadres: A (ji ǐ), B (yǐ), C (bǐng), D (D ǜ ng), E (w ǐ), G (G ǜ ng) and Xin (X ǜ n). Among them, A, C, E, G and E are dry in the sun, while B, D, G, G and G are dry in the shade.

Twelve earthly branches: Zi, Ugly, Yin, Mao, Chen, Si, Wu, Wei and Shen. Among them, Zi, Yin, Chen, Wu, Shen and Xu are Yang branches, and Ugly, Mao, Si, Wei, You and Hai are Yin branches (note: the twelve branches correspond to the zodiac-Zi: Mouse; Ugly: cattle; Yin: Tiger; Thumb: rabbit; Chen: Dragon; Rudder: snake; Afternoon: horse; No: sheep; Shen: Monkey; Hey: chicken; Hey: dog; H: pigs. )。

The predecessors said: "Heaven is dry, while wood is dry, and strength is yang;" Branches, branches of trees, weak and cloudy. "It can be seen that it is called the original intention of the dry branch. [2]

Hours, the ancients divided a day into twelve hours, and each hour is equal to two hours now. According to legend, each time is named after the time of animals in the zodiac.

1. China traditional time unit. Divide a day and night into twelve sections, each called an hour, which is now two hours. Twelve hours are named after earthly branches, starting from midnight, when it is midnight, it is midnight, when it is noon, it is noon. Song Su Shi's "Three Provinces and Six Feet Lakes Open": "The gate is under the jurisdiction of newly-built money, and it will be closed for an hour or two every high tide ... those who want to enter and leave the gate by public or private boats will not sit up until the gate is closed." Peach Blossom in a clear sky left: "The days are short and the nights are long, and it's three hours' journey." The second act of Wang Zhaojun written by Cao Yu: "Half an hour ago, he accompanied the son of heaven to dinner."