Solar term formula

The spring rain shakes the spring and clears the valley, and the summer is full of mountains and summers.

Autumn dew, autumn frost, little snow in winter and cold in winter.

The two festivals remain unchanged every month, with a maximum difference of one or two days.

The first half of the year is June 2 1 day, and the second half is August 23.

Twenty-four solar terms originated in the Yellow River Basin. As early as the Spring and Autumn Period, four solar terms were set, namely, mid-spring, mid-summer, mid-autumn and mid-winter. After continuous improvement and perfection, by the Qin and Han Dynasties, the 24 solar terms had been completely established.

In BC 104, the taichu calendar written by Deng Ping officially set 24 solar terms in the calendar, and defined the astronomical position of the 24 solar terms.

Solar terms refer to the twenty-four solar terms and climate, which is a supplementary calendar formulated by China in ancient times to guide farming, and is the crystallization of long-term experience and wisdom of working people in ancient China.

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.