Ask the weather question, how to calculate Fujiu?

Three days means "three days", and there are "three days" in a year. From summer to the future, the third Geng Day is the first Geng Day, the fourth Geng Day is the middle Geng Day, and the first Geng Day after beginning of autumn is the last Geng Day. Also known as the dog days, it is the hottest day of the year.

In the lunar calendar used in China, there is a kind of "stem-branch calendar", which uses 65,438+00 characters of "heavenly stems" (A, B, C, D, E, G, Xin, nonyl and decyl) and "earthly branches" (Zi, Ugly, Yin, Mao, Chen, Si and Wu). According to the provisions of the "Law of the Day of the Cadre and Branch", the third Geng day from summer to the future is the starting day of initial lodging, the fourth Geng day is the starting day of intermediate lodging, and the first Geng day after beginning of autumn is the starting day of final lodging, which stipulates that the initial lodging and final lodging are 65,438+00 days respectively. According to this rule, midsummer in some years is 10 days, and midsummer in some years is 20 days.

Modern calendars are rarely marked with "trunk and branch" calendars, so it is generally not obvious that that day is "Geng Day" and it is necessary to look up the "Yellow Calendar". The summer solstice of 20 10 is June 2 1 day (the main branch is Renyin), and the first Geng day after that is June 29 (the main branch is Geng Xu). Then, the third Geng Day is July 19 (Gengwu), which is the first day of the first autumn, and the fourth Geng Day is July 29th.

If that day in beginning of autumn happens to be Geng Day, then it should start from the next Geng Day, not from the day in beginning of autumn. Take 20 12 as an example. 20 12 beginning of autumn on August 7th, the main branch of that day was "Geng Zi", and the last day was the next "Geng Day" on August 7th. Because every year in beginning of autumn, whether it's August 7th, 8th or 9th, if that day happens to be "Gengri", then this "Gengri" will start at 23:00 the day before, that is, it will arrive at Gengri first and then start in autumn, so the first "Gengri" after "beginning of autumn" will be ten days later.