What is the basis for determining the ambush?

Entering volts means entering "three volts". There is a folk saying that "early autumn occurs in summer solstice", which is the basis of establishing early autumn. The almanac stipulates that "the summer solstice sunset is on the third Geng day", which means "counting down from the summer solstice" and then falling asleep on the third Geng day. The "Geng Day" here refers to the days prefixed with "Geng" in the ancient "Ganzhi Jiri Law". [6] The so-called "heat of three volts" can be divided into front, middle and back volts. Its date is determined by the solar term date and the dry consumption date. The climate in dog days is characterized by "high temperature and high humidity", because the southeast wind blows in dog days and the air is humid. The humidity of the wind caused the humidity in the dog days. 【 4-5 】 The date of "Geng Day" is changeable in the Gregorian calendar, so the accommodation date is different every year, but the accommodation date is always between July 1 1 and July 20th in the Gregorian calendar. The fourth day of the fourth day to the fifth day of the fifth day; The first Geng Day to the second Geng Day after beginning of autumn is the last time. Every Geng day is 10 days apart, and the number of summer days is not fixed. Between the summer solstice and the beginning of autumn, there are four Geng days, including summer 10, summer 5 Geng days and 20 days.