The Origin of Twenty-four 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.

Some people think that the 24 solar terms are subordinate to the lunar calendar, but they are actually defined according to the solar calendar. That is, according to the position of the sun on the ecliptic, a year is divided into 24 equal parts. That is to say, the ecliptic is divided into 24 equal parts, each equal part accounts for 15 of the ecliptic. Because the time required for the sun to pass through each bisection is almost equal, the Gregorian calendar dates of the 24 solar terms are roughly the same: the first half of the year is around 6 and 2 1, and the second half is around 8 and 23. And there are two formulas: 621 in the first half of the year and 823 in the second half.

In ancient times, solar terms were called "qi", and there were two qi in each month: the former was called "solar terms" and the latter was called "neutral qi". The monthly distribution of the 24 solar terms is shown in the following table, which is closely related to the arrangement of the lunar leap month. In the lunar calendar, beginning of spring is the first of the 24 solar terms. The names of the 24 solar terms are named according to the place pointed by Dougang and the natural climate and landscape at that time. The so-called fighting means that the three stars of the Big Dipper, Kuixing, Xingxing and Yuxing, point to different directions and positions with the movement of celestial bodies, and the positions they refer to are the months they represent. For example, the first month is cloudy, dusk refers to cloudy, midnight refers to cloudy, and daytime refers to cloudy. February is the base, at dusk, at midnight, during the day, and so on.