There are 24 solar terms 节气 (jié qì) in China. The 24 solar terms were determined by the changes of the sun’s position in the zodiac throughout the year. A complete orbit of the sun is divided into 24 segments with each segment lasting about half a month. In the lunar calendar, the date of each solar term is basically fixed with minor changes within one or two days. As a reflection of the regularity of the changes of the climate in the areas of the middle and lower reaches of the Yellow River, the 24 solar terms are still being used by farmers.
These are used for the 24 seasonal exercises, like these: