The origin of the 24 solar terms is very simple.

Twenty-four solar terms are an important part of the ancient calendar in China, reflecting the changes of the four seasons when the earth revolves around the sun. According to the position change of the sun in a year and the evolution sequence of the ground climate caused by it, the ancient people in China divided the 365 1/4 days of a year into 24 segments, and each segment was divided into 12 months to reflect the four seasons, temperature and phenology. This is the twenty-four solar terms.

In the western calendar, there are only four solar terms: vernal equinox, summer solstice, autumn equinox and winter solstice, which correspond to the four moments when the sun crosses the equator twice, with the northernmost and southernmost as the center of the four seasons. In China, there are 24 solar terms in the lunar calendar. The names of solar terms mostly reflect the starting point and midpoint of phenology, farming time or season, which is obviously based on the convenience of farming time.

The 24 solar terms reflect the seasonal phenological characteristics of the middle and lower reaches of the Yellow River Basin. As early as the Spring and Autumn Period, four solar terms, namely, mid-spring, mid-summer, mid-autumn and mid-winter, were set, and they have been continuously improved. By the Qin and Han Dynasties, the 24 solar terms had been completely established. In BC 132, the book Huainanzi recorded the names of 24 solar terms, which is the earliest and most complete record ever seen. The ancients called the 24 solar terms distributed at the beginning of the first month of the summer calendar "solar terms" and the solar terms in the middle of the month "zhongqi", meaning meteorology and climate.