Why did it arrive at Qingming on October 6th after winter 106?

106 From the solstice after beginning of winter to Qingming, this is the Qingming time according to the ancient solar terms before the constitutional calendar of the Qing Dynasty. The winter solstice in 2009 is 65438+February 22nd. According to the calculation of 106 days, Tomb-Sweeping Day should be April 7th of Gregorian calendar 20 10 (Gregorian calendar, that is, the present Gregorian calendar), but actually Tomb-Sweeping Day was April 5th two days ago. The distance from winter solstice to Qingming is 104 days.

The reason is that the calculation method of solar terms was reformed in Qing Dynasty. It turned out to be an algorithm of flat solar terms, and later it was renamed as fixed solar terms. The solar term is simply to divide the tropical year into 24 equal parts. The first thing that can be determined is the "two solstices", namely the winter solstices and the summer solstices. In winter solstice, the sun reaches the tropic of Capricorn, and the daytime is the shortest; From summer solstice, the sun reaches the Tropic of Cancer, and the night is the shortest. Winter solstice and summer solstice are easier to measure. The longest day in a year is the winter solstice, and the shortest is the summer solstice. It is stipulated that the time from the winter solstice to the next winter solstice is one year (the year of the tropic of cancer). A year is divided into twenty-four "qi", which is called twenty-four solar terms. At that time, due to the lack of astronomical knowledge, the flat gas was divided equally by time. From the solstice of winter, there is air every once in a while, such as cold, rain, vernal equinox and so on. , called gas; The other 12 species, such as: slight cold, beginning of spring, fright, etc. , are called solar terms.

Let's verify it through literature. "Chronicle of Jingchu's Age" said: "Last winter festival, there was a flurry of rain, which was called three days of cold food without fire." In other words, there is a gap of 105 days from winter solstice to cold food. The Cold Food Festival, also known as "No Smoking Festival", "Cold Food Festival" and "Hundred Fifth Festival", is the 105th day from summer to the future, one or two days before Tomb-Sweeping Day. In other words, Qingming is between 106 and 107 from the winter solstice. There are seven solar terms between Tomb-Sweeping Day and the winter solstice, one of which is 365.38+079 days earlier than Tomb-Sweeping Day. Divide the tropical year by 24 and multiply it by 7, and the Qingming time before the constitutional calendar of the Qing Dynasty is about 106.5 days, which is consistent with the Qingming record between the winter solstice 106- 107 days.

It was later discovered that because the earth's orbit around the sun is elliptical. Near the sun, the speed of the earth's revolution is faster, but far away, it is slower. For the Central Plains region where this calendar was made at that time, some solar terms could not reflect the real climate. For example, the vernal equinox is not necessarily a geographical vernal equinox. Therefore, since the Qing Dynasty, the vernal equinox has been set at 0 degrees, and every time the sun runs 15 degrees on the ecliptic, it is set as a solar term or neutral gas. This preparation method is called "fixed gas method" and has been used up to now. Its calculation method is complex and needs professionals. Nevertheless, we can use the data of these two years to sum up: the winter solstice in 2009: 201:47, the Qingming Festival on February 22nd, 5: 3 1, and the distance on April 4th, 65438+3: 44; On February 22nd, the winter solstice is 20 10: 65438+7: 39, the Qingming Festival is 2010:12: 00, and the distance is 104: 33.

That is to say, modern Tomb-Sweeping Day is about 104. 1 day from the winter solstice, but it is before the cold food.

For example, Tomb-Sweeping Day at 20 10 is April 5th of the Gregorian calendar (now Gregorian calendar), and the Cold Food Festival is April 6th of the Gregorian calendar.