The earliest solar terms in China

As early as the Spring and Autumn Period and the Warring States Period, people in China had the concepts of Solstice in the South and Solstice in the North. 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 give each equal part a proper noun, that is, twenty-four solar terms. 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. 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.

The earliest calendar is Xia Li, which is said to belong to Xia Dynasty.

In the Western Han Dynasty, in 104 BC, the taichu calendar compiled by Deng Ping officially set 24 solar terms in the calendar, and defined the astronomical position of the 24 solar terms. Taichu calendar is the first complete calendar.