This is the terminology used in birth dates. The so-called birth date means that the four time units of year, month, day, and hour at the time of birth are represented by the heavenly stems and earthly branches respectively. One time unit is represented by a heavenly stem and an earthly branch. One earthly branch represents, then the four time units of year, month, day and hour are combined with four heavenly stems and four earthly rulers to record the time, which is eight characters, so it is called the birth date eight characters. For example, today at this time (sishi is 9 o'clock - For people born at 11 o'clock), their birth dates are: Bingshen (year), Dingyou (month), Renzi (day), and Yisi (hour). The yen refers to the heavenly stem that represents the day when you were born. In the above example, it is Ren (ri), and the yen earthly branch is the earthly branch that cooperates with the ren day, which is also the child. By the way, let’s talk about the concept of earthly branches. The earthly branches are actually the 12 zodiac signs we call, namely Zichou, Yinmao, Chen, Siwu, Weishen, Youshuhai. If the 12 earthly branches are matched with the year, they are the annual branches. If they are matched with the month, they are the monthly branches. If they are matched with the day, they are the yen earthly branches, which are referred to as the daily branches (today's yen earthly branches are the children). If they are matched with the time, they are the hour branches.
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