Source of solar terms

Twenty-four solar terms originated in the Yellow River basin and were established on the basis of climate and phenology in this area. As early as the Spring and Autumn Period, four solar terms were set, namely, mid-spring, mid-summer, mid-autumn and mid-winter. By the end of the Warring States Period, solar terms had eight names: beginning of spring, Equinox, Long Summer, Summer Solstice, beginning of autumn, Equinox, beginning of winter and Winter Solstice. 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.