When did the twenty-four solar terms appear? Why are there 30 in Qi?

Our existing 24 solar terms originated from the Yellow River Basin, which is the long-term accumulated experience and wisdom of working people in ancient China. The wise ancients in the Spring and Autumn Period roughly defined the solar terms such as midsummer, midsummer, midsummer and midwinter, and then constantly improved and perfected them on this basis. Twenty-four solar terms were completely established in Qin and Han Dynasties.

Because the China lunar calendar is a kind of "Yin-Yang calendar" based on the movement of the sun and the moon, the lunar calendar can't fully reflect the solar cycle. However, China's agricultural and social characteristics need a strict understanding of the operation of the sun, and farming and crop planting should be carried out in full accordance with the sun, so a relatively accurate time period is needed for guidance.

Because the main political, economic, cultural and agricultural activity centers in China are mostly concentrated in the Central Plains of the Yellow River Basin in history, the guiding time period, that is, the formulation of solar terms, needs to be formulated according to the location, so 24 solar terms * * * are added to the calendar as the criterion for leap months. Twenty-four solar terms can reflect the changes of seasons, guide agricultural activities and have a far-reaching impact on people's food, clothing, housing and transportation. The 24 solar terms are divided according to the position of the sun on the ecliptic.

It is said that Qi has thirty solar terms, which is related to its geographical location and climate characteristics. The 24 solar terms reflect the Central Plains, mainly Shaanxi, where the temperature is moderate, the precipitation is obvious, the winter is warm and humid, and the four seasons are distinct. Shandong, where Qi people live, is close to the ocean, with short spring and autumn and long duration in winter and summer. It is necessary to divide the short spring and autumn seasons more carefully in order to give people a more accurate timetable for farming operations.