When did the heat start?

The hot summer begins from summer to the third Geng day in the future and ends on the day before the second Geng day after the beginning of autumn, usually between the hot summer solar terms and the hot summer solar terms. The solar calendar is from the middle of July to the middle of August.

The intense heat, also called "dog days", is the expression of the hottest period in a year in China calendar. Summer heat is divided into three stages: initial stage, middle stage and final stage. According to the formula of "the third night in summer", autumn begins on the third night after summer, that is, the first day of the first autumn. The first Geng Day after beginning of autumn is the first day of the last autumn.

The formula of "Xia San Gengzi" began on the third Gengzi Day in Xia Hou, that is, the first day of the first autumn. The first Geng Day after beginning of autumn is the first day of the last autumn. The first and last days are 10 days. The alto is between the first volt and the last volt, lasting 10 days or 20 days.

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. There are four Geng days between the summer solstice and the beginning of autumn, with 10 days in midsummer and 20 days in five Geng days. So some years dog days are 30 days, and some years are 40 days.