How are solar terms divided?

China has successfully formulated and used the lunar calendar since ancient times, so the 24 solar terms should naturally be subordinate to the lunar calendar! In fact, the 24 solar terms are purely solar calendars. Why?

When analyzing the significance and changes of the twenty-four solar terms, we can clearly find that the cycle of the twenty-four solar terms is based on the cycle of spring, summer, autumn and winter, which is a reflection of the earth's rotation around the sun. Because human beings live on the earth, they can't feel the movement of the earth, but they see the sun moving in the starry sky, which runs just once a year. We call this movement of the sun a visual movement, and the path it runs is called the ecliptic. The ecliptic is a great circle with a circumference of 360 degrees. The twenty-four solar terms are to divide the ecliptic into 24 segments, each of which is 15 degrees. Every time the sun moves 15 degrees (actually, the earth moves around the sun 15 degrees), it means 1 solar term. The time it takes the sun to complete each segment is basically the same, so the date of the 24 solar terms in the Gregorian calendar has hardly changed. For example, Tomb-Sweeping Day is around April 5th every year, and the winter solstice festival is around 65438+February 22nd every year. The dates of the 24 solar terms in the solar calendar can be summarized in two sentences, namely: the first half of the year is from June to February;

Come eight, two and three in the second half of the year;

Only a day or two before and after.

There is a discrepancy of 1 to 2 days before and after, which is caused by the uneven speed of the sun.

The date of the twenty-four solar terms of the lunar calendar is very uncertain; Because the year of the lunar calendar is about 1 1 day less than the return, the date of the same solar term in a certain year is about 1 1 day later than the previous year. For example, Tomb-Sweeping Day in 1978 is February 28th, while Tomb-Sweeping Day in 1979 is March 9th. The leap year is about 384 days in the lunar calendar, which is about 19 days older than the return. As a result, the solar term date of next year is about 19 days earlier. For example, the lunar calendar 1979 is a leap year, and Tomb-Sweeping Day 1980 is advanced to February 19. It can be seen that in the lunar calendar, the date of solar terms will not be known without consulting the calendar, and the date of solar terms every year will be determined through complicated calculations.