The ancient calendar of China was divided into heavenly stems and earthly branches, or earthly branch for short. Ten stems are A, B, D, D, E, G, F, N, N, and twelve branches are the noon application of Zi Chou Yin Mao Tatsumi.
Birthdates calculation method: first determine your birthday, it is best to know the birth time, and then look up the corresponding branch name in the perpetual calendar.
Time calculation: In ancient times, a day was divided into twelve hours, two hours were one hour,11:00-1:00 was a sub-hour,1:00 was an ugly hour, and so on. The time name is the same as the twelve branches.