What is the dog days?

In ancient China, "Fu" meant hot weather. Every year, the beginning of "Fu" days in the northern hemisphere is mostly after the slight summer heat and before the great summer heat. According to the astronomical calendar, the "volt" days are "three volts", which are called "head volt", "middle volt" and "last volt" (also called one volt, two volts and three volts), totaling 30 to 40 days.

Generally speaking, the beginning of "Fu" is determined by the date of the solar term and the date of the dry year. According to the ancient chronology of China, the starting date of "Fu Tou" must be the third boxer day after "Xia" (one boxer is 10 day), which means that "the third boxer in summer is Fu". The third day marked with "Geng" is the day when "Fu Tou" begins, such as 1997 July 17. When it passed through heaven and earth, it was the day of "Geng Shen", which happened to be the day when the third Geng Day began, that is, the day when "Fu Tou" began. It must be emphasized here that this kind of cooperation in heavenly stems and earthly branches began thousands of years ago, and when this cycle is scheduled to be1July of 997 Gregorian calendar 17, it happens to be the "Geng Shen" day, not the temporary cooperation of that year. Usually, the annual "summer solstice" usually falls on June 2 1-22, and the individual year falls on June 23.

Based on this, the "head drop" (also known as the initial drop) over the years began in mid-July. According to the Chronology of Ganzhi, the fourth Geng day from summer to the future is the day when "Zhongfu" begins. The first "Geng" day after "beginning of autumn" is the start date of final lodging, that is, the final lodging is subject to the solar term "beginning of autumn", so it is not necessarily 10 day from lodging to final lodging. At the same time, the chronology of trunk and branch also stipulates that the "head" and "tail" are each fixed as 10 days. If there is any change, it is only in the number of days of "upper middle school". "Noon" is either 10 day or 20 days, and it is absolutely not allowed to have "odd days" like noon 1 1 day, 12 day or 13 day. So the number of days in midsummer is either 30 or 40.

This year is July 15, with an incubation period of 40 days. He entered the ambush on July 20 last year, and the ambush period was only 30 days.

Why are the dog days different in length?

"Fu" is divided into initial fu, middle fu and final fu. There is a saying in agricultural proverbs that "you are three years old on the summer solstice, and you will fall after autumn". According to the trunk and branch calendar, "A, B, C, D, E, Ji, Geng, Xin, Ren and Gui" has a Geng Day every 10 day. June 2 1 day this year is the summer solstice and the "Bingzi Day" of the lunar calendar. According to this calculation, July 15 happens to be the third Geng day, so this year's July 15 falls. But the entry date is different every year. July 15 this year is Voldemort Day, and the same day next year can't be Geng Day in either solar or lunar calendar.

The third Geng Day after long summer is the lodging day, the fourth Geng Day starts in the middle, and the first Geng Day after beginning of autumn starts at the end. Therefore, the length of the incubation period mainly depends on the intermediate incubation period. Generally speaking, it takes 47 days from summer solstice to autumn. In general, the middle festival is 10 days after July of 19, and the middle festival is 20 days before July of 18. The fourth Geng Day from this summer to the future is July 25th, and it begins to be in the middle. The first Geng Day after beginning of autumn is August 14, which starts at the middle of 20 days.

Every Geng day is 65,438+00 days apart, and the number of mid-festival days is not fixed. There are four Geng days from summer solstice to autumn, with 65,438+00 days in the middle, six Geng days and 20 days in the middle.

The third Geng sunrise from this summer to the future is now in July 15, and it begins to set in July 15. July 25th is the first day of middling, and there are five more days from summer to the future this year, so middling is 20 days.