Why are the 24 solar terms called the lunar calendar?

The summer solstice and the winter solstice refer to the longest day and the longest night respectively, which are collectively called "the second solstice" and "the solstice" is the extreme.

vernal equinox and autumnal equinox refer to two days as long as day and night respectively, which are collectively called "bisection" and stand for "equal share".

beginning of spring, long summer, beginning of autumn and beginning of winter are collectively called "four stands", and "stand" means "start".

24 solar terms is a part of the lunar calendar, which is essentially a Gregorian calendar. Now the Gregorian calendar is also a Gregorian calendar, which naturally coincides with each other. The lunar calendar is a combination of yin and yang, and because of the composition of the lunar calendar, there is a big gap with the prevailing Gregorian calendar.

24 solar terms is native to the Yellow River Basin and is based on the temperate monsoon climate characteristics in this latitude zone. However, China has a vast territory and diverse climatic resources, so it can't be applied to 24 solar terms in large areas outside the Central Plains, such as temperate continental climate in Xinjiang and Inner Mongolia, subtropical monsoon climate in Yunnan, Guangxi and the southeast coast, plateau mountain climate in Tibet, tropical monsoon climate in Hainan and southwestern Yunnan and Guangxi.