How did you come up with the 24 solar terms?

In order to keep the return year of the lunar calendar in sync with the Gregorian calendar, the ancients adopted the method of setting leap months. There were 24 solar terms in the ancient calendar, which were divided into solar terms and neutral atmosphere. The lunar calendar is angry twice a month. The beginning of the month is called solar terms, and after the middle of the month is called qi. "For example, beginning of spring is the first month's solar term, and rain is the first month's gas." The average length of the two solar terms in Gregorian calendar is 30.5 days, while that in Lunar calendar is only 29.5 days, with a difference of 1 day. So the monthly weather will be 1-2 days later than last month. If this goes on, there will always be a month when there is only solar terms and no gas. This non-neutral month is defined as "leap month" by the calendar and is called "leap month". This year's leap month is after July, which is leap July. Why is there no leap in the first month? This is because the earth's orbit around the sun is an ellipse, and the sun is at a focus of the ellipse. In a year, the distance between the earth and the sun is near and far. When the earth is far away from the sun, it moves slowly around June in Gregorian calendar, so the interval between the two gases is longer, exceeding 3 1 day at the longest. According to the average length of the previous 30.5 days, there is a great possibility that there is no gas in the middle of the month and there is a great possibility of a leap month. So there are many opportunities in April, May and June. Around 65438+February in Gregorian calendar, the earth moves fast and the neutral gas interval is short. The shortest is only a little more than 29 days, which is shorter than one month in the lunar calendar. Therefore, it is unlikely that neutral gas will not appear in January, November and December. Relatively speaking, there are fewer opportunities for leap months. The ancient calendar has 24 solar terms, which are divided into solar terms and neutral atmosphere. The lunar calendar is angry twice a month. The beginning of the month is called solar terms, and after the middle of the month is called qi. "For example, beginning of spring is the first month's solar term, and rain is the first month's gas." The average length of the two solar terms in Gregorian calendar is 30.5 days, while that in Lunar calendar is only 29.5 days, with a difference of 1 day. So the monthly weather will be 1-2 days later than last month. If this goes on, there will always be a month when there is only solar terms and no gas. This non-neutral month is defined as "leap month" by the calendar and is called "leap month". This year's leap month is after July, which is leap July.