Are the 24 solar terms based on the lunar calendar or the solar calendar?

The 24 solar terms are divided according to the solar calendar.

The current 24 solar terms are a knowledge system formed by observing the movement of the sun for a year and understanding the changing laws of seasons, climate and phenology in a year. It divides the orbit of the sun in one year into 24 equal parts, corresponding to a certain position reached by the sun every time it runs 15 on the ecliptic, and each equal part is a "solar term".

Extended data

Spring and Autumn Equinox, Summer and Winter Solstice and Global Seasonal Variation

1. From the vernal equinox to the autumnal equinox, it is summer in the northern hemisphere and winter in the southern hemisphere. During this period, the northern hemisphere has long days and short nights, while the southern hemisphere has short days and long nights. The north pole is in the extreme day and the south pole is in the extreme night; The height of the sun north of the Tropic of Cancer is always greater than the average, while the height of the sun south of the Tropic of Cancer is less than the average.

2. From the autumnal equinox to the winter solstice and then to the vernal equinox, the northern hemisphere is in the winter half year and the southern hemisphere is in the summer half year. During this period, the length of day and night, the extreme value of day and night and the height of the sun in the northern and southern hemispheres are contrary to the above situation. North of the Tropic of Cancer, the sun rises from the horizon in the southeast and sets on the horizon in the southwest.

3. From summer solstice to winter solstice, from summer to winter in the northern hemisphere and from winter to summer in the southern hemisphere. During this period, the days in the northern hemisphere are getting shorter and shorter, the nights are getting longer and longer, and the extreme day area is getting smaller and smaller. In the southern hemisphere, the days are getting longer and longer, the nights are getting shorter and shorter, and the polar night zone is getting smaller and smaller.

4. From winter solstice to summer solstice, from winter to summer in the northern hemisphere and from summer to winter in the southern hemisphere. The changes of the length of day and night, the extreme value of day and night, and the height of the sun in the northern and southern hemispheres are contrary to the above situation. North of the Tropic of Cancer, the rising direction of the sun changes from southeast to northeast, and the setting direction changes from southwest to northwest.

5. From the winter solstice to the vernal equinox, and from the summer solstice to the autumnal equinox, the number of days around the world is close to the average (12 hour), and the range of extreme days and nights is gradually narrowing. The height of the sun north of the Tropic of Cancer and south of the Tropic of Capricorn is close to the average. North of the Tropic of Cancer, the rising direction of the sun gradually approaches due east, and the setting direction approaches due west.

6. From the vernal equinox to the summer solstice, and from the autumnal equinox to the winter solstice, the length of day and night all over the world is changing to an extreme value, and the range of extreme day and night is gradually expanding. The height of the sun north of the Tropic of Cancer and south of the Tropic of Capricorn also tends to be extreme. North of the Tropic of Cancer, the rising and setting directions of the sun move to the northeast, southeast, northwest and southwest respectively.

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