Preside over solar terms

12 solar ballad: At the beginning of spring, rain spread along the river. Frightened crows, the spring equinox is dry. Qingming is busy planting wheat, and Grain Rain is busy farming. Long summer goose feathers live, birds come here. Mango seeds were shoveled away, but cotton was not harvested on the solstice in summer. The summer heat is not hot, but the summer heat is in the dog days.

Beginning of autumn is busy playing indigo, and busy sharpening knives and sickles in summer; After a thousand years of land cutting, there is no field in the autumn equinox. The cold dew is not cold, and the first frost has changed. Beginning of winter fief, Xiaoxue River fief, Daxue River fief, there is no boat from winter to the sun, with slight cold and severe cold for three or nine days.

Solar terms refer to the special festivals in the dry calendar that indicate seasons, phenology, climate change and the establishment of "December construction". At first, the solar terms were determined by the direction of the top of the bucket handle of the Big Dipper. The current 24 solar terms are divided according to the position change of the earth on the ecliptic (the earth's orbit around the sun).

Each node corresponds to a location where the earth reaches every 15 times on the ecliptic. It is a knowledge system formed by observing the movement of the sun in a year and understanding the changing laws of the four seasons, climate and phenology in a year.