A dog day is 10 days. The dog days, which appear between the hot summer and the hot summer, are the days with the highest temperature, humidity and sultry weather in a year.

The so-called "dog days" refers to the "dog days" of the lunar calendar, which is the hottest period of the year. The time of accommodation is not fixed every year, and the length of accommodation is also different. You need to check the almanac to calculate it. Simply put, we can use the formula of "Xia San Geng" to express the lodging date, that is, from the third Geng day in Xia Hou, the initial lodging is 10 day, the intermediate lodging is 10 day or 20 days, and the final lodging is 10 day.

As the old saying goes, "The third Geng Day after long summer is the first day (the time of falling), and the first day after beginning of winter is the start time of 19. The old saying is well said, well said.

"The third Geng Day after long summer is the time starting point of the first Geng Day, the fourth Geng Day after long summer is the time starting point of the first Geng Day, and the first Geng Day after beginning of autumn is the time starting point of the last Geng Day. It can be seen that the start time of dog days is closely related to the emergence of Geng Day from summer to the future.