Month corresponding to spring, summer, autumn and winter
Spring refers to the period from beginning of spring to long summer in the China lunar calendar, including six solar terms: beginning of spring, Rain, Sting, Equinox, Qingming and Grain Rain. Summer refers to the period from long summer to beginning of autumn, including six solar terms: long summer, small full, busy, summer solstice, light summer and great summer.
Autumn refers to the period from beginning of autumn to beginning of winter, including six solar terms: beginning of autumn, Chushu, Bailu, Autumnal Equinox, Cold Dew and First Frost. Winter begins in beginning of winter in the lunar calendar and ends in beginning of spring in the following year. It includes six solar terms: beginning of winter, light snow, heavy snow, winter solstice, slight cold and severe cold.
The origin of the four seasons
Our earth constantly revolves around the sun, and at the same time, it also revolves around its own axis. However, the earth axis is not perpendicular to the track plane, but has an inclination angle of 23 degrees and 27 minutes. It is precisely because of this tilt that the direct point of the sun on the earth's surface moves between the Tropic of Cancer and the Tropic of Capricorn, thus forming four seasons: spring, summer, autumn and winter.
When the sun shines directly on the Tropic of Cancer, the northern hemisphere gets more solar heat, and the day is longer than the night, so the highest temperature in the northern hemisphere is summer. At this time, the sun is slanting in the southern hemisphere, and the southern hemisphere gets less solar heat and the night is longer than the day, so the southern hemisphere is in the coldest season of the year-winter.
When the earth makes another half turn around the sun, the direct point of the sun moves from the Tropic of Cancer to the Tropic of Capricorn, and the solar heat gained by the northern hemisphere gradually decreases, from summer to autumn, and then to winter. On the other hand, the southern hemisphere goes from winter to spring, and then to summer.