When does the dog days start counting?

Dog days are the hottest time in summer. Dog days make people conform to nature, move less, lie prone more, and cultivate themselves.

Dog days of 20 12: It first appeared in July of 14, lasted for 10 days, and ended on July 23rd; 20 days in the middle of July 24th and ending on August 12. The last day of August 13, lasting 10 days, ended on August 22nd.

However, there is also a saying that the "trunk-branch calendar" was popular in ancient China, and 60 groups of different names matched with 10 heavenly stems and 12 earthly branches were used to record dates for recycling. The day with the word "Geng" is called "Geng Day". The word "Geng" in Geng Day is the seventh word in "A, B, C, D, E, Ji, G, Xin, Ren, Gui" 10 day, and it is repeated every 10 day. Starting from the summer solstice, according to the date of trunk, the third Geng day is the first, the fourth Geng day is the middle, and the 1 th Geng day after beginning of autumn is the last. When there are four Geng days between the summer solstice and the beginning of autumn, the middle part is 10 days, and when there are five Geng days, the middle part is 20 days. It seems that the emergence of Gengri will affect the length of the first half sooner or later, so there will be 30 days in some years and 40 days in some years.