The Autumnal Equinox, also known as the September Equinox or the first day of fall in the Northern Hemisphere, occurs every year either on September 22 or September 23. This day marks the moment when the sun is directly above the equator while moving from north to south, and also the astronomical beginning of Fall in the Northern Hemisphere.
Learn more about the Start of Fall.
"Equinox" derives from two Latin words, aequus and nox, and it means "equal night". This is because, during an equinox, day and night are around the same length in terms of duration. This happens because the sun is above the equator line for 12 hours during an equinox. It is exactly at the moment that the sun crosses the equator line that the Autumnal Equinox happens.
As the seasons go from Summer to Fall, after the Autumnal Equinox the days become shorter and nights grow longer, as the sun rises at a later time and sets earlier during the autumnal months.
While the September Equinox usually falls on September 22 or 23, due to the number of days that it takes the Earth to orbit the sun, and the way the Gregorian Calendar is organized, the equinox can sometimes fall one day earlier or later. However, this is very rare and the next time the Autumnal Equinox is set to happen on September 24 is 2303.
Around the Autumnal Equinox, there is a full moon known as the "harvest moon". As the night sets earlier during fall, the full moon closest to the equinox allows farmers to work later into the evening.
Autumnal Equinox Celebrations
Many cultures around the world commemorate the arrival of fall with ancient traditions and rituals. Civilizations such as the Druids and the Mayans were already celebrating the equinox centuries ago, as usually, the changing of the seasons meant that the harvest season was soon to arrive.
Wiccans, druids, and pagans who still observe the traditions surrounding the Autumnal Equinox, flock to Stonehenge in England every year to observe the sunrise and perform their rituals. Paganism knows the equinox as the Second Harvest, or Mabon, a day to thank the summer and welcome the coming darkness. People who observe the Second Harvest build altars with offerings of fruits and vegetables for their gratitude rituals. They also take this time to donate food to the needy.
In Canada and United States, even people who do not practice the Mabon rituals have their own traditions and activities that begin around the Autumnal Equinox. The arrival of fall marks the beginning of country fairs and festivals, the preparation for Halloween with the harvesting of pumpkins, and giving thanks for all the food that the harvests have produced during Thanksgiving.