Solar terms in China

Solar terms refer to the 24 solar terms and climate, which is a supplementary calendar made by China to guide farming in ancient times. 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. China's orthodox twenty-four solar terms are based on Henan.

Solar term date speed algorithm: general birthday formula -[y× d+c]-l y = year, D=0.2422, L= leap year, and c depends on solar term and year. The C value of beginning of spring in this century is 4.475, and the date of beginning of spring in 20 17 is as follows: [2017× 0.2422+4.475]-[2017/4-15] = 492-489.