"crouching" means being forced to hide underground, which is the hottest season in a year. . Starting from the summer, according to the arrangement of dry and branch days, the third Geng Day is the first month. The fourth Geng Day was in the middle, and the first Geng Day after beginning of autumn was the last. The word "Geng" on Geng Day is the seventh word in ten days of "A, B, C, D, E, Ji, Geng, Xin, Ren and Gui", and Geng Day is repeated every ten days.

The start and end time of the dog days is different every year, roughly from mid-July to mid-August. How exactly is it worked out? China's popular "Ganzhi Diri method" records dates with 60 groups of different names, and each day with the word Gengzi is called Gengri.

During the Qin and Han dynasties, there was a popular saying that "the five elements are mutually reinforcing". People think that the hottest day in summer belongs to fire, while Geng belongs to gold. Gold is afraid of being melted by fire, so on Geng Day, gold will be hidden. Therefore, it is stipulated that from summer to the third Geng day in the future, it is the initial lodging (with 10 day), and from summer to the fourth Geng day in the future, it is the intermediate lodging (with 10 day in some years and 20 days in some years), and the first Geng day after beginning of autumn is the final lodging, also known as the final lodging (with 10 day).

When there are four Geng days between summer solstice and the beginning of autumn, the middle part is 65,438+00 days, and when there are five Geng days, the middle part is 20 days. So sometimes it is ten days from the middle to the end, sometimes it is twenty days, and both "head" and "tail" are 65,438+00 days.