What are solar terms?

The solar terms are 24 solar terms. Since the slight cold, every 30-degree increase in the solar meridian is another solar term. There are slight cold, beginning of spring, Jingzhe, Qingming, Changxia, Mangzhong, Xiaoshu, beginning of autumn, Bailu, Hanlu, beginning of winter and Daxue. It's called twelve solar terms.

There is a song in the twenty-four solar terms: Spring rains shake the spring and clear the valley, and summer is full of mountains and summer is connected with heat. Autumn dew, autumn frost, little snow in winter and cold in winter.

From the Han Dynasty to the end of the Ming Dynasty, the solar terms divided by the method of "smoothing qi" are divided into three periods, which shows the general situation of astronomy, geography, personnel and nature in the Yellow River Basin. The solar terms of "leveling method" start from the shortest winter solstice in the Yellow River basin, and the 24 solar terms start from the winter solstice to the end of heavy snow.

"Twenty-four solar terms" reflect the influence of the sun on the earth and belong to the solar calendar category. It is a knowledge system formed by observing the movement of the sun in a year and understanding the changing laws of the four seasons, climate and phenology in a year.

It not only plays a guiding role in agricultural production, but also affects the food, clothing, housing and transportation of ancient people, and even cultural concepts. The current lunar calendar absorbs the solar terms of the trunk calendar as a supplement to the calendar, and is adjusted to conform to the tropic year through the leap method, forming a combined calendar of yin and yang.