What Time, Date Is Fall Equinox 2021? Rituals to Celebrate From Around the World

This Wednesday, September 22, will mark the fall or autumn equinox for 2021—a signal that summer in the Northern Hemisphere has come to a close.

The equinox means that the sun will be positioned exactly above the Earth's equator. This will take place at around 3:21 p.m. EDT, according to EarthSky.

This positioning of the sun means that day and night will last about the same time, as opposed to the summer when days are longer and the winter when days are shorter. Indeed, the word equinox comes from the latin aequus, "equal," and nox, "night."

Equinoxes, like the solstices, occur because the Earth is tilted slightly on its side as it orbits the sun. This means that at some parts of the year the northern half gets more sunlight and warmth than the southern half, and vice versa. This is why Australia experiences summer at the same time as the U.S. experiences winter.

Ancient cultures noticed that throughout the year, the sun tended to rise and set in a slightly different position in the sky throughout the year.

In the Northern Hemisphere, for example, one may notice that the sun is shifting towards the south as summer comes to a close.

On the equinoxes, the sun rises and sets along the path of the equator.

Having made note of this annual phenomenon, ancient cultures placed a significance on the fall equinox—though it meant different things to different people.

To ancient Greeks, the fall equinox marked the return of the goddess Persephone to her husband Hades in the underworld.

For some Japanese Buddhists, the fall equinox coincides with the Higan holiday in which people return to their hometowns to pay respects to their ancestors.

Elsewhere, the fall equinox was a time to celebrate food and harvests. In ancient China, for example, people would celebrate a successful harvest of rice and wheat around this time, as did people living in the U.K.

There are also artificial landmarks still standing today that are thought to relate to the sun's path across the sky throughout the year. Stonehenge, in England, is a popular one, though it's usually associated with the solstices rather than the equinoxes.

In Mexico, tourists still flock to the pyramid at Chich'en Itza every equinox. It was built in dedication to Kukulkan, a feathered serpent god who returns to Earth on the equinoxes to provide blessings for harvests, according to legend.

The pyramid is built such that, on the equinoxes, it casts a shadow that represents a snake crawling down the temple.

Another modern tradition is the Chinese Mid-Autumn Festival, also called the Mooncake Festival, which still takes place across China and has roots in harvest celebrations.

This year, occurs on Tuesday, September 21. The mid-autumn festival also takes in New York City.

Earth orbiting sun
A stock image shows an illustration of the Earth orbiting the sun, along with other planets of the Solar System. Equinoxes occur because of the Earth's tilt. johan63/Getty