Chapter 31 The second quarter of the twenty-four solar terms

Although the average length of the lunisolar calendar is close to the return year, the compensation method is a bit abrupt because it takes more than three years to add a leap month, and the climate change cannot be fully reflected in the lunisolar calendar.For example, Lixia, which means the beginning of summer, is in March this year, and it may be April next year, and the relationship with the order of the month is not fixed.In agricultural countries, people pay special attention to the time of sowing and harvesting, and it is difficult to popularize the calendar that cannot reflect the seasons. Therefore, the twenty-four solar terms came into being.

The specific names of the twenty-four solar terms are: Lichun, Rain, Jingzhe, Vernal Equinox, Qingming, Grain Rain, Lixia, Xiaoman, Grain in Ear, Summer Solstice, Slight Heat, Great Heat, Liqiu, End of Heat, White Dew, Autumnal Equinox, Cold Dew, Frost’s Descent, Lidong, Light Snow, and Big Snow , Winter Solstice, Minor Cold, Great Cold.Among them, those in even numbers, such as rain, vernal equinox, grain rain, etc., are also called Zhongqi. Solar terms, in essence, divide the orbit of the earth around the sun into 15° parts, 24 parts for a total of 360°, and each solar term represents a fixed position on the orbit.In terms of time, due to the uneven speed of the earth's revolution, some solar terms have 14 days, and some have nearly 16 days, with an average of more than 15 days.As we all know, seasons are a reflection of the earth's revolution, so solar terms can more accurately represent the phenomenon of climate change and warmth.

The twenty-four solar terms can be divided into four types according to the meaning of their names: (1) There are eight solar terms representing the four seasons: Lichun, Vernal Equinox, Lixia, Summer Solstice, Liqiu, Autumnal Equinox, Lidong, and Winter Solstice. (2) There are five solar terms that represent the degree of coldness and warmth: Slight Heat, Great Heat, End of Heat, Minor Cold, and Great Cold. (3) There are seven solar terms that represent the amount of precipitation: rain, grain rain, white dew, cold dew, frost, light snow, and heavy snow. (4) The four solar terms related to farming are Jingzhe, Qingming, Xiaoman, and Grain in Ear.

The twenty-four solar terms belong to the Gregorian calendar system, and it is used in conjunction with the synodic month, which is a major feature of the Chinese lunar calendar.