How to calculate the ambush?

From midsummer to the third Geng day in the future, it began to lurk.

In ancient China, heavenly stems and earthly branches was used to record time. The figures of heavenly stems mainly include A, B, C, D and E, while the figures of earthly branches mainly include Zi, Ugly, Yin and Mao. Heavenly stems and earthly branches, Jia Zi, Yi Chou, Bing Yin, Ding Mao, etc. And cross them 60 times, so it's called Jiazi. "Three Geng" refers to meeting three characters of "Geng" and falling into an ambush on the third Geng day, that is, the first ambush.

The date of Geng Day is changeable, not fixed, so the accommodation date is different every year, but the accommodation date is always between July 1 1 and July 20. The fourth to fifth Geng Day is moderate, and the first to second Geng Day after beginning of autumn is the end.

Every Geng day is 65,438+00 days apart, and the number of mid-festival days is not fixed. There are four Geng days from summer solstice to autumn, with 65,438+00 days in the middle, five Geng days and 20 days in the middle.