The origin of the autumnal equinox solar terms How did the autumnal equinox solar terms come from?

1. Every year on September 22nd or 23rd, when the sun reaches longitude 180 degrees, it directly hits the equator of the earth, so a day is divided into 24 hours, each 12 hours, and there is no polar day and night phenomenon in the world. This is the midpoint of ninety days in autumn. After that day, the days in the northern hemisphere became shorter and the nights became longer.

2. According to China's ancient beginning of spring, Changxia, beginning of autumn and beginning of winter, the four seasons are divided. The autumnal equinox lives in autumn for 90 days and divides the autumn equally. At this time, 24 hours a day are divided equally, each 12 hours. On the day of the "autumnal equinox", the sun is almost directly at the equator. After that, the position of direct sunlight moved south, and the days in the northern hemisphere were short and the nights were long.