When did the solar term Song come out?

Since the Western Han Dynasty, the twenty-four solar terms have been used in the solar terms Song Dynasty. As early as the Spring and Autumn Period, people already had the concept of four seasons: spring, summer, autumn and winter. Twenty-four solar term song was written by Meng and Xiao Yun.

During the Warring States Period, Shi Shen of Wei compiled an astrolabe, which included 28 stars and five planets: Jin Mu, water, fire and earth. This is the first star map in the world, which indicates that China astronomy has entered a new era.

The solar calendar is calculated according to the time required for the earth to revolve around the sun once. The lunar calendar is based on the cycle of the moon.

In order to fully reflect the changes of seasonal climate, as early as the Zhou Dynasty and the Spring and Autumn Period, ancient astronomers used the method of "earth rules" to determine the vernal equinox, summer solstice, autumn equinox and winter solstice.

According to the position change of the sun on the ecliptic and the evolution order of the ground climate in a year, the whole year is divided into 24 equal parts, and each equal part is named, which is the origin of the 24 solar terms.