The autumnal equinox

The autumnal equinox is one of the twenty-four solar terms. 

It starts around September 23rd each year, when the sun reaches 180 degrees (autumnal equinox) at the Douzhiyou. 

In the "Explanation of the Seventy Two Seasons of the Moon": 

"In the middle of the eighth month, the autumn equinox is observed." 

"The equinox is equal, and this is half of the ninety days, so it is called the equinox." 

The equinox is half, which is the midpoint of the ninety days in autumn.

Phenomena on Earth

The sun shines almost directly on the equator, and thereafter the direct point of 

the sun continues to move southward, hence the autumnal equinox, also known as the equinox.

At the autumnal equinox, the world has equal length of day and night. 

After the autumnal equinox, the days in the northern hemisphere gradually shorten and 

the nights gradually lengthen, while in the southern hemisphere, the days and nights gradually shorten. 

After the autumnal equinox, the range of polar nights near the North Pole gradually increases 

from the North Pole, and the range of polar days near the South Pole gradually increases from the South Pole.

In the ancient Chinese book "The Flowing Dew of Spring and Autumn, the Entry and Exit of Yin and Yang", it is said: 

"The autumnal equinox is a combination of yin and yang, so the day and night are evenly divided while the cold and heat are flat.

" The meaning of "autumnal equinox" is twofold: firstly, the sun reaches 180 degrees on the yellow path at this time, 

and the day and night are evenly divided 24 hours a day, with 12 hours each; Secondly, according to 

the ancient Chinese seasonal division system that began with the beginning of spring, beginning of summer, beginning of autumn, 

and beginning of winter, the autumnal equinox falls within 90 days of autumn, dividing autumn equally. After the autumn equinox, 

the temperature gradually decreases, so there are sayings such as "White Dew Autumn Equinox Night, Cold Night",

 "One Autumn Rain, One Cold Night, Ten Autumn Rain Put on Cotton", 

and "In August, the Wild Goose Gate opens, and the Wild Goose bring frost under their feet".

The autumnal equinox is also a beautiful and pleasant season, 

with a pleasant breeze and sunshine, a refreshing autumn sky, and a fragrance of osmanthus. 

Spring planting and autumn harvest, Tang poet Li Shen's "Compassionate Farmers" 

says that planting a grain of millet in spring, harvesting ten thousand seeds in autumn, flowering in spring, and bearing fruit in autumn. 

During the autumnal equinox season, the fruits are abundant, with crabs, fish, and shrimp being plump, and golden chrysanthemums turning yellow. 

The autumnal equinox was also an important solar term in agricultural production during the time of wheat planting. 

If the south has just cooled down at this time, farming can continue until the end of autumn when frost falls.