Autumn Equinox, the sixteenth of the twenty-four solar terms, is the fourth solar term of autumn. Doo refers to the You; the sun reaches 180° of yellow longitude; in the annual calendar September 22-24 intersection of the festival. Autumn equinox on this day the sun almost directly to the earth's equator, the day and night around the globe equal length. Autumn Equinox, "points" that is, "equal parts", "half" meaning, in addition to the day and night equal parts, there is a layer of meaning is equal parts of the fall. After the autumnal equinox, direct sunlight position south, the northern hemisphere day is shorter than the night is longer, the temperature difference between day and night increases, the temperature decreases day by day.

The autumnal equinox was once a traditional moon festival, and the Mid-Autumn Festival evolved from the "Autumn Eve Moon Festival".

On June 21, 2018, the State Council on the agreement to set up the "Chinese Farmers' Harvest Festival" was released, agreeing that from 2018 onwards, the autumnal equinox will be set up every year as the "Chinese Farmers' Harvest Festival".