In ancient times, 24 solar terms were used to divide seasonal changes. How did it come into being?

The 24 solar terms are determined by the natural changes of seasons, climate and phenology.

1.The establishment of 24 solar terms

During the Qin and Han Dynasties, the 24 solar terms were completely established and divided. In BC 104, taichu calendar, which was founded by Deng in Han Dynasty, officially set 24 solar terms in the calendar, and defined the astronomical position of the 24 solar terms. According to the available data, the 24 solar terms may occur at the end of the Warring States Period. Although the names of all the 24 solar terms only appeared in Huainanzi Astronomical Training in the Western Han Dynasty, most of the names of the 24 solar terms were recorded in the book Huainanzi Astronomical Training in the Warring States Period.

2. 24 solar terms

The ancients determined the beginning and end of four solar terms according to the laws of heaven and earth, and divided 24 solar terms. The orbit of the sun in one year is divided into 24 equal parts, and each equal part is equal to a "solar term", which is collectively called "24 solar terms". Twenty-four solar terms represent twenty-four different positions of the earth on its rotation orbit.

3. Twenty-four solar terms sequence

Because it takes 365 days for the earth to go around the sun, there is a solar term every fifteen days, and each solar term represents different changes in climate, phenology and time. Spring rains shake spring, clear valleys, and summer is full of summer. Autumn cold, first frost, winter snow. The familiar "Song of Songs" in China implies the order of the 24 solar terms.

Therefore, the 24 solar terms also depend on calendars, such as accurate calendars, brother calendars, solar calendars and monthly calendars. And become a guide to measure the progress of agricultural production.