The algorithm of ambush time is as follows: ambush is to enter the dog days.
That is, from summer to the third Geng day in the future, the first lodging is 10 day, the middle lodging is 10 day or 20 days, and the last lodging is 10 day.
The dog days are the hottest thirty or forty days in a year in the Central Plains. The dog days are calculated according to the lunar calendar, between the middle and late July and the early August of the solar calendar.
The length of accommodation is not fixed every year, and the length of accommodation is also different.