What are the reasons for the division of the 24 solar terms?

The division of solar terms fully considers the changes of natural phenomena such as seasons, climate and phenology. At the same time, it also reflects the annual apparent movement of the sun, so in the current Gregorian calendar, the dates of solar terms are basically fixed, with the 6th and 2 1 in the first half of the year and the 8th and 23rd in the second half of the year, with a difference of no more than 1-2 days.

The basis for the classification of the twenty-four solar terms.

The first category reflects the seasons. Among them, beginning of spring, Changxia, beginning of autumn, beginning of winter, vernal equinox, autumnal equinox, summer solstice and winter solstice are used to reflect seasons, and a year is divided into four seasons: spring, summer, autumn and winter. The vernal equinox, autumnal equinox, summer solstice and winter solstice are divided from an astronomical point of view, reflecting the turning point of solar height change. Beginning of spring, Changchun, beginning of autumn and beginning of winter reflect the beginning of the four seasons.

The second category reflects climate characteristics. The five solar terms of slight summer heat, great summer heat, slight cold and severe cold reflect the change of temperature and are used to express the degree of heat and cold in different periods of the year; The four solar terms of rain, Grain Rain, light snow and heavy snow reflect the phenomenon of precipitation, indicating the time and intensity of rainfall and snowfall.

The third category reflects phenological phenomena. Xiaoman and awn species reflect the maturity and harvest of related crops; Frightening and Qingming reflect natural phenology, especially stinging. It uses the first thunder in the sky and the revival of underground stinging insects to inform everything in the world that spring is coming back to the earth.