The algorithm is as follows: Lodging means entering the dog days, that is, from summer to the third Geng day in the future, the first dog days are 10, the middle dog days are 10 or 20, and the last dog days are 10.
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.
Accommodation time
The lodging time is not fixed every year, and the length of summer varies. The lodging date can be simply expressed by the formula of "three boxer days on the summer solstice", that is, from the third boxer day after the summer solstice, the first lodging is 10 day, the summer is 10 or 20 days, and the last lodging is 10 day.
In ancient China, the method of "counting days by branches" was popular, and 65,438+00 days and 65,438+02 plots were used to record 60 groups of different days for recycling. The day with the word "Geng" is called "Geng Day". The word "Geng" on Geng Day is the seventh word in "A, B, C, D, E, Ji, Geng, Xin, Ren and Gui" on 10 day, and it is repeated every 10 day on Geng Day.