When is the autumnal equinox in 2023?

The autumnal equinox in 2023 is on Saturday, September 23, 2023, the ninth day of the eighth lunar month.

The autumnal equinox is the sixteenth solar term among the twenty-four solar terms and the fourth solar term in autumn. The sun reaches longitude 180, and the festival is held on September 22-24 of the Gregorian calendar every year.

The autumnal equinox symbolizes the autumn harvest, most crops mature in autumn, and the autumnal equinox also symbolizes the joy of autumn harvest. The autumnal equinox means that in the middle of autumn, the length of day and night is equal. The autumnal equinox divides day and night equally, and the sun is on the horizon all day. After the autumnal equinox, the direct sunlight moves south, the days in the northern hemisphere become shorter, the nights become longer, and the temperature drops, which is of universal significance throughout the country.

According to the lunar calendar, "beginning of autumn" is the beginning of autumn, "the first frost" is the end of autumn, and the "autumnal equinox" is exactly half of the 90 days from beginning of autumn to the first frost, so the arrival of the autumnal equinox season symbolizes that half of the autumn season has passed.

Astronomical calendar

On the day of the autumnal equinox, the point of direct sunlight reaches the longitude 180 (autumnal equinox), almost directly to the equator of the earth, and the length of day and night is the same all over the world (regardless of the refraction of sunlight by the atmosphere and the dim shadow in the morning).

After the autumnal equinox, the direct point of the sun continued to move from the equator to the southern hemisphere, and the days in the northern hemisphere began to shorten and the nights became longer, that is, the days in a day began to be shorter than the nights; The southern hemisphere is the opposite. Therefore, the autumnal equinox is also called the landing point. At the North Pole and South Pole, on the day of the autumn equinox, the sun is on the horizon all day.

In the same solar term, every year is 6 hours or 5 hours later than the previous year, and the leap year is 24 hours earlier. In this way, the date reflects that the same solar term remains unchanged or lags behind the previous year 1 day; The leap year remains unchanged or is earlier than the previous year 1 day.

In this way, the starting point of the same solar term has three different Gregorian calendar dates. Take the "autumnal equinox" as an example, there are three situations: September 22nd, September 23rd and September 24th.