How to calculate heavenly stems and earthly branches formula?

1, annual dry formula: annual dry = year single digits -3 (applicable to any year in AD, single digits are less than or equal to 3, borrow 10).

Take 20 19 as an example, its single digit is 9,9-3 = 6, which means that the heavenly stems are their own.

2. Annual expenditure formula: the remainder of annual expenditure = (year +7)÷ 12 (divisible by remainder 0, that is, remainder 12= ugly).

Taking 20 19 as an example, the remainder of (20 19+7)÷ 12 is 10, that is, the ground branch is Hai.

Extended data:

The operation cycle of Tiangan is ten, with ten hours, ten days, ten months and ten years as different cycles, which are repeated in an orderly manner and form a stable periodic law. The running cycle of the earthly branch is twelve, with twelve hours, twelve days, twelve months and twelve years as different cycles, which are repeated in an orderly manner, forming a stable periodic law.

With heavenly stems and earthly branches's cooperation, we created cycles of 60 hours, 60 days, 60 months and 60 years, and repeated them in an orderly manner, forming a stable periodic law. Because the cycle of heavenly stems and earthly branches's cooperation starts from the heavenly stem "A" and the earthly branch "Zi", people call this cycle with 60 as a process "Jia Zi".

Baidu Encyclopedia-heavenly stems and earthly branches