The story of vernal equinox and the legendary story of vernal equinox in the twenty-four solar terms

1, 4000 years ago, Xi Zhong was sent by Emperor Yao and came to Wendeng Shili Village. After a lot of investigation and analysis, according to the astronomical phenomenon that birds and stars are seen in the south at dusk, the time of vernal equinox is determined, which lays the foundation for the determination of four seasons and the final formation of twenty-four solar terms. It is not a legend that Xi Zhong arrived in Gushan. Yao in Shangshu records "the life of Zhai _ Yi and Yue _ Gu".

2. In fact, the vernal equinox was born in the Yellow River valley, which is one of the 24 solar terms. We see that "rain" and "fear" are inserted into the bisector between beginning of spring and the vernal equinox. These two names describe the meteorological or biological characteristics of the first half of spring.

It's going to rain, and the little life hiding in the ground for the winter will start to wake up when it hears the call of the sun. Between the vernal equinox and the long summer is "Qingming" and "Grain Rain".

4. From the rainy season, we can know the climate of Tomb-Sweeping Day. Literally, we can know from Grain Rain that this is the season when crops need rain to promote their growth. Insert "Xiao Man" and "Busy" between the long summer and the summer solstice.

5.24 solar terms are defined by 24 equal angles of the great circle that the sun passes through in the sky, not by 24 equal hours of a year, so the time intervals are not equal. According to the approximate number of days, some are 15 days, and some are 16 days.

6. Therefore, how to divide the months in a year can express the 24 solar terms succinctly and accurately enough, so that they can be arranged in the simplest rules, which is convenient for people to remember and master. This is an important task in calendar design.