Why is the vernal equinox the second solar term in autumn?

"Minute" means that the length of day and night is equal, and it is also the middle of spring and autumn; "Solstice" means that the hottest day in summer and the coldest day in winter are coming. They are the longest day, the shortest night, the shortest day and the longest night respectively.

Twenty-four solar terms are the development stages of 24 phenological temperature changes. Each of the 24 solar terms has a clear meaning. Climate change is mainly determined by the solar heat obtained on the earth. There are eight solar terms, such as beginning of spring, Spring Equinox, Long Summer, Summer Solstice, beginning of autumn, Autumn Equinox, beginning of winter and Winter Solstice. Among them, "Li Si" means the beginning of spring, summer, autumn and winter.

Twenty-four solar terms are divided into 24 segments according to the position change of the earth in orbit and the evolution order of the ground climate when it revolves around the sun. The first day of January is called the solar term, and the middle of January is called Zhongqi.

Section means section, which refers to a period of temperature phenological change, and qi refers to meteorological climate. "Qi" reflects the ancient thought that the changes of four seasons are all caused by the changes of "Qi". The earth revolves around the sun 360 degrees, and the vernal equinox is zero. Every 15 degree is a solar term, 365 days a year, with an average of each solar term 15 days.