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

Twenty-four solar terms appeared as early as the Spring and Autumn Period and were not formally established until the Qin and Han Dynasties. In the period of Emperor Wu of the Han Dynasty, the 24 solar terms were formally incorporated into the calendar and began to be implemented. The formation of the 24 solar terms did not appear and be established overnight, but it took a long time to finally run in. This is the agricultural wisdom summed up by our ancestors through labor and experience. In the process of running-in, the most obvious case is the thirty solar terms used by Qi, which is gradually formed due to Qi's unique geographical location and climate factors.

According to Guanzi, the state of Qi implements the four-season farming busy October system, with three months in each season, while the whole year is 360 days and ten months, and there are 36 days in a month. Each of these 30 solar terms is 12 days, in which the cycle of spring ploughing and agricultural harvest is 96 days, which specifies the specific time and days of farming busy.

These 30 solar terms can be divided according to seasons. There are eight solar terms in spring and autumn, and even fewer in Xia Dong in the second quarter, with seven solar terms each. According to historical records, the eight festivals this spring are "local atmosphere, small weather, loyalty, Qingming, beginning, middle and lower"; The seven solar terms in summer are "less sputum, exhaled breath, middle sputum, middle sputum, light summer arrival, heatstroke and late summer"; The eight autumn festivals are "wind arrival period, little hair period, white dew period, restoration period, pre-festival, early hair period, middle hair period and down hair period"; The seventh solar term in winter is "the beginning of cold, slight cold, moderate cold, moderate cold, severe cold, the yin of severe cold and the end of severe cold".

So why are there such thirty solar terms different from other vassal States? You know, Qi is located on the coast of East China, which is now Shandong. More than half of its territory extends into the sea, belonging to a typical warm temperate monsoon climate, which is humid and warm all the year round. However, because the coastal areas are easily affected by the differences in thermal properties between land and sea, the spring and autumn of Qi Dynasty are short and long. In order to make better use of the short spring and autumn seasons, Qi people use solar terms to divide the spring and autumn seasons, so there is one more solar term than the spring and autumn season, that is, the eighth and seventh festivals of the spring and autumn period, which is the origin of the thirty solar terms of Qi.