Twenty-four solar terms are gradually defined and integrated in China. During the Zhou Dynasty and the Spring and Autumn Period in China, the summer solstice, winter solstice, vernal equinox and autumn equinox were determined by measuring the sun shadow with soil gauge. Later, the number of solar terms recorded in Lu Chunqiu of Qin Dynasty increased to eight, namely, beginning of spring, Spring Equinox, Long Summer, Summer, beginning of autumn, Autumn Equinox, beginning of winter and Winter. In addition, there are records of 1 month, February, May, July, July and September. These are the seeds of solar terms. By the Han Dynasty, the twenty-four solar terms had been recorded in Tian Zi Xun in Huainan (a collection of Liu An and others in BC 139), which was the same as the current twenty-four solar terms, indicating that the twenty-four solar terms were complete between Qin and Han Dynasties. About 2 100 years ago.