Why is Tomb-Sweeping Day on the fifth day of the fourth lunar month every year?

Calendar proverb: "March is sunny in Grain Rain". Of these two solar terms, Grain Rain Festival is in the middle of March, and it must be in March, so March is also called "Grain Rain Month". If Grain Rain Festival is not in March, a leap month can be arranged. According to the average weather, Tomb-Sweeping Day is on the day before Grain Rain 15.7/32 (a little more than half a month), because the calendar only requires Grain Rain to be in March, but it is not stipulated on the tenth day and that day, so Tomb-Sweeping Day is not necessarily in March. In 2004, the second day of the fourth month (02: 1 1) in Grain Rain was not in the third month, so the third month was arranged as a leap month and named as "leap February". What about Qingming? So it falls on leap February 15 (18: 59). The distance between them is 15.3/ 10 day calculated by constant gas. (> normal air 15.7/32 days. )

According to the Gregorian calendar, the dates of the 24 festivals are relatively fixed. Qingming is usually on April 4 or 5. According to the statistics of 2 1 century, there are 32 times on the 5th and 68 times on the 4th in a century. Tomb-Sweeping Day in 2004 was on April 4th.

By the way, the Gregorian calendar date table of 24 solar terms included in various handbooks at present only represents the last century. For a long time, the date of solar terms also changed. Nothing in the world is static. As far as Xiaoman is concerned, the last century paid attention to February 2 1 and February 22. 2 1 century, a century-old boy met 44 times on the 20th, 56 times on the 20th, 0 times on the 22nd, and never appeared again on the 22nd.