When is it hot in summer?

Summer begins from summer to the third Geng Day in the future and ends the day before the second Geng Day after beginning of autumn, usually between the solar terms of summer and summer, and the solar calendar is from mid-July to mid-August.

Summer heat, also known as "dog days", is the manifestation of the hottest period in a year in China's old calendar. Xia Fu is divided into initial Fu, middle Fu and final Fu. According to the formula of "three boxer in midsummer", the third boxer day after midsummer is the first day. 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 middle lie is between the initial lie and the final lie, which is 10 day or 20 days.

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. When there are four Geng days between the summer solstice and the beginning of autumn, the middle part is 10 days, and the appearance time of five Geng days is 20 days. So in dog days, some years are 30 days, and some years are 40 days.