Ganzhi is the ancient calendar of China, which originated in the Western Han Dynasty and prevailed in the late Eastern Han Dynasty. The lunar calendar is still in use. The year, month, day and time of a person's birth are represented by branches, so it is called "eight characters", also called "birthday".
In the lunar calendar, the stems and branches are arranged in turn, such as Jia Zi and Yi Chou. Sixty years is a cycle and can be recycled. Tiangan is a branch of A, B, C, D, E, G, Xin, Man and Ghost. There are twelve earthly branches: Zi, Chou, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu and Hai.
The meaning of birthday
Birthday plays an important role in Han folk beliefs, and ancient Han astrologers calculate people's fate accordingly. The expression of the eight characters is four pillars of Japanese law, four pillars of lunar law, or four pillars of Japanese law and lunar law.
In order to get the correct birth time, the ancient Han people thought that the sundial instrument was the most accurate measurement during the day. When the clock time is the artificial average time and the regional standard, it is necessary to calculate the "apparent solar time difference" according to the solar terms (ecliptic) and the "local longitude time difference" according to the place of birth, so as to get the real astronomical birth time.