Tomb-Sweeping Day, why is the time not fixed?

1. Because the length of a year is determined by the movement of the sun, and the 24 solar terms are also determined by the position of the sun, basically the date of each solar term will not change much every year. However, the time that the earth orbits the sun is called the "tropic year". The actual length of a tropical year is 365.2422 days, and the Gregorian calendar year is 365 days, so there will be 0.2422 days more each year, and the specific time of solar terms will be "delayed" by 0.2422 days each year. In this way, the cumulative time after 4 years is 0.9688 days, almost one day. In order to correct mistakes, there is a "leap year" system in the Gregorian calendar, with one more day on February 29th every four years. If the solar term is delayed from midnight to the next day, or advanced to the previous day due to leap year, the date of the solar term will change, but the date difference will only be within three days.

According to astronomical experts, in recent decades, the date of Qingming has been changing from April 4 to 6. Statistics show that the Qingming date of 190 1 to 1943 is April 5 or 6; April 5 1944 to1975; 1976 by mid-2000, there was a leap year on February 29th, April 4th in Tomb-Sweeping Day, and 5th in other years; In the 20 years since 2008, every leap year and the Qingming Festival of the following year are April 4. For example, in 2008 and 2009, 20 12 and 20 13, 2020 and 202 1, the Qingming date in 2024 and 2025 is April 4.

Second, Tomb-Sweeping Day date calculation formula

(Y*D+C)-L

Interpretation of the formula: Y= two digits after the number of years, D=0.2422, L= leap year, 2 1 century C=4.8 1, and 20th century C=5.59.

For example, the Qingming date in 2088 = (88× 0.2422+4.81)-(88/4) = 26-22 = 4, then April 4, 1988 is Qingming.

Third, Tomb-Sweeping Day, also known as the outing festival, is at the turn of mid-spring and late spring. Tomb-Sweeping Day is a traditional festival in China, and it is also one of the most important sacrificial festivals. It is a day to sweep graves and worship ancestors. Tomb-Sweeping Day is a traditional festival of the Chinese nation, which started in the Zhou Dynasty and has a history of more than 2,500 years. Through the historical development and evolution, Tomb-Sweeping Day has extremely rich connotations, and different customs have been formed in different places, with sweeping graves to worship ancestors and hiking as the basic themes.

The name of Tomb-Sweeping Day is related to the meteorological and climatic characteristics at this time. According to the Western Han Dynasty's "Huainanzi Astronomical Training", "Fifteen days after the vernal equinox, fighting refers to B, the wind is clear"; "Qingming Wind" is a refreshing and clear wind. "When I was in 100 questions" said, "Everything grows at this time, clean and bright. So it is called Qingming. " "Almanac": "On the fifteenth day after the vernal equinox, the bucket refers to Ding, which is used for Qingming, when everything is clean and bright, and when it is covered, everything is clean and bright, hence the name." As soon as Qingming arrives, the temperature rises and the earth presents a beautiful scene of spring. At this time, everything "spits out the old and absorbs the new".

Tomb-Sweeping Day is one of the important "eight festivals a year" in China. Generally, it is around April 5 of the Gregorian calendar, and the festival is very long. There are two sayings: 8 days before 10 and 10 days before 10, and these 20 days belong to Tomb-Sweeping Day. Tomb-Sweeping Day originally meant grave-sweeping day, and the government of the Republic of China designated 15 days after the vernal equinox in 935 as a national holiday, also known as the national grave-sweeping day. Tomb-Sweeping Day, Dragon Boat Festival, Spring Festival and Mid-Autumn Festival are also called the four traditional festivals in China. On May 20th, 2006, with the approval of the State Council, Tomb-Sweeping Day announced by the Ministry of Culture of China was included in the first batch of national intangible cultural heritage list.