How to calculate the ambush? From what date?

On the third Geng day after the summer, it began to fall. Until the end of the day before the second Geng Day after beginning of autumn. The dog days are divided into the first day, the second day and the last day. The first day begins from summer to the third Geng Day in the future, the second day begins from the fourth Geng Day, and the last day begins from the first Geng Day after beginning of autumn. The first and last days are 65,438+00 days, and the middle days may be 65,438+00 days or 20 days, because the third Geng day after the summer solstice solar term will appear sooner or later.

Introduction to Fukuda:

An ambush is entering the dog days. Three volts is divided into morning, middle and evening, which is the hottest time of the year. The dog days appear every year from mid-July to mid-August in the solar calendar, and their climatic characteristics are high temperature, low pressure, high humidity and low wind speed. "Fu" refers to being forced to hide underground by the sun's spirit, and the date of three volts is determined by the date of solar terms and calendar. Because every Geng day is 10 days apart, the stipulated time of the first day and the last day is 10 days.