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The Sun's rays line up perfectly with the Earth's equator

When is the autumn equinox in 2024?

The autumn equinox is the moment when the Sun passes the Earth's equator and for one nanosecond the Earth is neither tilted toward nor away from the Sun.


The autumn equinox explained

In astronomical terms, the equinox occurs the moment the Sun passes Earth’s celestial equator. The exact opposite of this is the spring or vernal equinox, which occurs at the same moment six months earlier...or later.

Back on Earth, the autumn equinox signifies more than just the beginning of shorter days and longer nights. It marks the last dying throes of the summer, the end of harvest, and the start of cooler, autumnal days when the leaves turn, heralding the start of winter. Obviously, for those in the Southern Hemisphere, the exact opposite occurs and autumn is comparable to the Northern Hemisphere’s spring.

A graphic showing the Earth's rotation around the sun, the cause of the seasonal equinox.

When is the autumn equinox?

The autumn equinox usually occurs on the 22nd or 23rd September, but it has been known to occur on the days on either side of those dates. A 21st September equinox has not happened for several millennia, but in the 21st century it’ll happen twice in five years, once in 2092 and again in 2096.

1931 was the last time the autumn equinox happened on 24th September, and it’s not due again until 2303.

In 2024, the Autumn Equinox will occur on Sunday, 22nd September at approximately 12:44pm GMT.

Where does the word equinox derive?

Unsurprisingly, the word ‘equinox’ is of Latin origin, with the former ‘equi’ aspect meaning ‘equal’ and the latter ‘nox’ meaning ‘night’. In the UK we call the new season ‘autumn’, while in the US they opt for the much simpler ‘fall’ inspired by the widely-seen falling leaves. Either way, for thousands of years, the autumn equinox hasn’t passed unnoticed, so let’s jump in and see what all the fuss is about.

Facts about the autumn equinox

1. If the Earth didn’t rotate on a tilted axis of 23.4 degrees, we wouldn’t have seasons, let alone an autumn equinox. This means the temperatures would be the same throughout the year and the day would always be equidistant to night.

2. During the autumn equinox, which lasts a nanosecond (not a day) the Earth isn’t tilted towards the Sun or away from it. For one split second, it lies in perfect balance, just like the balanced scales that symbolise Libra. According to astronomers, the autumn equinox is the moment the Sun enters the sign of Libra.

3. The full moon that occurs closest to the autumn equinox is called the ‘harvest moon’. This, in effect, provides an extra day via a bright night to gather in the remaining harvest before the weather turns and the crops rot in the ground. What’s known as the ‘full corn moon’ occurs on the rare occasion the harvest moon is in October because it's the time to gather the corn harvest.

4. Day and night are not precisely 12 hours each on the day of the autumn or spring equinox as it’s commonly believed. In the Northern Hemisphere, because of the refraction of sunlight, the Sun will appear to be above the horizon in some places, when it is actually below it.

5. The autumn equinox is the prime time for viewing the spectacular Northern Lights or Aurora Borealis. Due to the tilt of the Earth, solar winds and the particles of plasma that collide into atoms of oxygen, nitrogen and other components of the Earth’s atmosphere release photons that create one of nature’s most spectacular light shows.

6. In France, the autumn equinox marked the beginning of every new year between 1793 and 1805. The reason? Because the French monarchy was overthrown on 21st September, one day before the equinox in 1792. The new year returned to its original status after Napoleon was crowned Emperor of the French Republic.

Autumn equinox customs

Over the centuries, the autumn equinox has been celebrated in different ways across the world. In the UK, everyone will be familiar with the school harvest festival when food items are donated to help underprivileged households, a custom that derives from the Christian church and is celebrated on the Sunday closest to the harvest moon. The charitable aspect will be welcomed by many but is a relatively low-key event when we compare it to some of the following.


AKA ’The Catholic Feast of the Archangel Michael’ or ‘The Feast of Angels’ if you’re also acknowledging Gabriel, Uriel, and Raphael. It's celebrated on 29th September and involves eating nuts and goose. It’s believed that it was deliberately set close to the autumn equinox to appropriate the pagan celebrations that were taking place at the same time which may have been something like Mabon.


The provenance of Mabon appears to be neo-pagan and no more than 50 years old. However, gathering together all the fruit and crops (with the help of a harvest moon) around the autumn equinox in times of yore would be cause for some form of ritualised celebration. Just not one necessarily named after the god of Welsh mythology.

Snake of Sunlight in Mexico

The Mayan Pyramid of El Castillo plays host to a spectacular event that occurs on the day of both the autumn (and spring) equinox when the afternoon sunlight creates a shadow which resembles the body of a 120-foot-long snake on the western side of the main stairway. If you suffer from ophidiophobia, avoid it like the plague.

Autumn equinox in Greek mythology

The autumn equinox in Ancient Greece marked the start of autumn because Demeter, wife of Zeus and the goddess of the harvest, brought famine to the world after her daughter, Persephone, was abducted by Hades. When Hades returned Persephone to Demeter, she restored the failed crops and spring began again.

The Moon festival in China and Vietnam (or Chuseok in Korea)

During a lunar calendar, the Moon Festival occurs on the 15th day of the eighth lunar month. In other calendars, it’s held annually on the full moon nearest the equinox. The festival involves eating moon cakes, a delicacy made of thin pastry with a sweet, dense filling). A notable part of celebrating the holiday is the carrying of brightly lit lanterns.

Ohigan in Japan

No food or feasting during Ohigan. This is a time of meditation and reflection in the Buddhist calendar when the Japanese visit the graves of their ancestors and spend time with family. Here, the autumn and spring equinox symbolise the transition of life because the Sun sets directly west where, it’s believed, lies the afterlife.