Our ancestors determined which dynasty the 24 solar terms in a year belonged to.

As early as the Spring and Autumn Period and the Warring States Period, China was able to measure the length of the sun's shadow at noon with a soil gauge (a pole was erected on the plane), thus determining four solar terms: winter solstice, summer solstice, vernal equinox and autumn equinox. In a year, the shortest day of the noon soil return shadow is the summer solstice, the longest day is the winter solstice, and the shadow with moderate length is the vernal equinox or autumn equinox. The Book of History in the Spring and Autumn Period recorded the solar terms. The twenty-four solar terms are completely recorded in Huainanzi written by Liu An in the Western Han Dynasty. In ancient China, the lunar calendar was used to record time, and the solar calendar was used to divide the 24 solar terms of spring, summer, autumn and winter. Our ancestors called every five days and every three days as solar terms, and a year was divided into 72 days out of 24 solar terms.

Twenty-four solar terms originated in the Yellow River Basin. As early as the Spring and Autumn Period, the ancient sages of our country set four solar terms, such as midsummer, midsummer, midsummer and midsummer, and constantly improved and perfected them. 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. Twenty-four solar terms are the original cultural heritage of working people in China, which can reflect the changes of seasons, guide agricultural activities and affect the food, clothing, housing and transportation of thousands of households.