The origin of the twenty-four solar terms?

Twenty-four solar terms, a supplementary calendar to guide farming in ancient China, were formed in the Spring and Autumn Period and the Warring States Period. Because the lunar calendar in China is a kind of "yin and yang calendar", which is based on the movement of the sun and the moon, it can't fully reflect the solar cycle. But China is an agricultural society, and agriculture needs a strict understanding of the movement of the sun, so farming is entirely based on the sun. Therefore, the "twenty-four solar terms" that reflect the solar cycle alone are added to the calendar as the standard for determining leap months. Twenty-four solar terms can reflect the changes of seasons, guide agricultural activities and affect the food, clothing, housing and transportation of thousands of families. The twenty-four solar terms are divided according to the position of the sun on the ecliptic (that is, the orbit of the earth around the sun).

As early as the Eastern Zhou Dynasty, the Spring and Autumn Period and the Warring States Period, our people had the concepts of south to Japan and north to Japan. Subsequently, people divided the year into 24 equal parts according to the natural phenomena such as the running position of the sun and the moon at the beginning and middle of the month, the weather and the growth of animals and plants. And gave each division a proper noun, that is, twenty-four solar terms. By the end of the Warring States period, solar terms had eight names, including beginning of spring, vernal equinox, long summer, summer solstice, beginning of autumn, autumnal equinox, beginning of winter and winter solstice. These eight solar terms are the most important of the 24 solar terms. These eight solar terms mark the change of seasons and clearly divide the four seasons of the year. Later, when the book Huai Nan Zi was published, the names of the 24 solar terms were exactly the same as those of the modern ones.