Summer is over, where does autumn come from?

Autumn is here, and summer is not over yet. The sentence in Zhu Ziqing's Autumn in the Old Capital: Autumn has arrived, but summer is not over.

Every year around September 23rd, when the sun reaches longitude 180 degrees, it enters the "autumnal equinox" solar term.

The autumnal equinox, like the vernal equinox, is the earliest solar term established by the ancients. According to "Spring and Autumn Stories Yin and Yang Incoming", "The autumnal equinox is accompanied by Yin and Yang, so it is cold and hot day and night."

The meaning of the "autumnal equinox" has two meanings: First, in ancient China, four seasons were divided according to beginning of spring, Changxia, beginning of autumn and beginning of winter, and the autumnal equinox lived in autumn for 90 days and divided the autumn equally.

2. At this time, 24 hours a day are divided equally, each 12 hours. This day is the same as the "spring equinox" day. 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 became shorter and the nights became longer.