How did the 20 solar terms come from? What's the meaning?

The solar terms 1 and 24 originate in the Yellow River Basin. As early as the Spring and Autumn Period, there were four solar terms: midsummer, midsummer, midsummer and midsummer. After continuous improvement and perfection, by the Qin and Han Dynasties, the 24 solar terms had been completely established. In BC 104, the taichu calendar written by Deng Ping officially set 24 solar terms in the calendar, and defined the astronomical position of the 24 solar terms.

2. The time when the sun runs along the longitude of the Yellow River from zero degrees 15 degrees is called "a solar term". It runs 360 degrees every year, and * * * experiences 24 solar terms, twice a month.

3. Among them, the first solar term of each month is "solar term", that is, beginning of spring, Jingzhe, Qingming, Changxia, Mangzhong, Xiaoshu, beginning of autumn, Bailu, Hanlu, beginning of winter, Snow, Xiaohan, etc. 12 solar terms; The second solar term of each month is "Zhongqi", that is, there are 12 solar terms such as rain, vernal equinox, Grain Rain, Xiaoman, summer solstice, great heat, intense heat, autumnal equinox, first frost, light snow, winter solstice and great cold.

4. "Solar term" and "neutral gas" appear alternately, each lasting 15 days. Now people have called "solar terms" and "neutral gas" solar terms. Twenty-four solar terms reflect the apparent movement of the sun in one year, so the dates of solar terms are basically fixed in the current Gregorian calendar, with the first half of the year being 6 days and 2 1, and the second half being 8 days and 23 days, with a difference of 1 ~ 2 days.