Find out which dynasty had 24 solar terms a year.

As early as the Spring and Autumn Period and the Warring States Period, China was able to measure the length of the noon shadow with a soil gauge (a pole was erected on the plane) to determine the four solar terms: winter solstice, summer solstice, vernal equinox and autumn equinox. In a year, the shortest noon shadow is the summer solstice, and the longest is the winter solstice. A shadow of moderate length is the vernal equinox or autumnal equinox. The solar terms were recorded in Shangshu in the Spring and Autumn Period. Huai Nan Zi, written by Liu An in the Western Han Dynasty, completely recorded the 24 solar terms. In ancient China, the lunar calendar was used to record time, and the solar calendar was used to divide the 24 solar terms in spring, summer, autumn and winter. Our ancestors called five days to wait, three days to breathe, and a year was divided into 72 days.

Twenty-four solar terms originated in the Yellow River Basin. As early as the Spring and Autumn Period, the ancient sages of China put forward four solar terms, namely, midsummer, midsummer, midsummer and midwinter, and constantly improved and perfected them. By the Qin and Han Dynasties, the 24 solar terms had been completely established. In BC 104, taichu calendar, which was formulated by Deng Ping, officially set the 24 solar terms in the calendar, and defined the astronomical position of the 24 solar terms. Twenty-four solar terms were originally created by working people in China.