The four major annual events include two Solstices (summer and winter) and two Equinoxes (autumn and spring).
September 22nd is the official first day of autumn and is celebrated in the Pagan/Wiccan tradition as Mabon, the time of harvest, gratitude, and sharing. No doubt, the pagan tradition had a lot to do with the celebration of Thanksgiving in Canada and the US. However, the day divided into equal parts of dark and light, is an excellent marker for any tradition and, most countries to have some kind of harvest celebration.
The Autumnal Equinox is the basis for the myth of Persephone's return to the Underworld after a half year of growth and greenery. If you recall your Greek mythology, you'll know that Persephone was kidnapped by Hades (god of the underworld) to become his wife. Demeter, Persephone's mother and goddess of the harvest was understandably peeved. After a period of mourning and struggle, Demeter eventually got her daughter back from Hades, but only for nine months of the year. Every fall, Persephone would return to the underworld to spend three months with Hades. During these months, Demeter refused to use her divine skills to make plants grow, explaining why we have three months of winter every year.
In Christian tradition, the equinox is Michaelmas Day. Did you know you've been missing a reason to party? These days, Michaelmas is a minor festival mainly observed in the Catholic church. Centuries ago in England, the time around Michaelmas also had a business side. Servants were paid their wages after the harvest, and workers looked for new jobs at employment fairs which also became a place for celebrations.
And let us not forget The Mayan Snake of Sunlight. At the precise moment of the equinox, when the Sun shines directly on the equator, an enormous “snake of sunlight” slithers down the stairs of the main pyramid at Chichen Itza, Mexico. The Mayans who constructed this ancient temple used advanced astronomical calculations to determine the exact angle of the staircase.
Japan has the Higan Festival, China and Vietnam celebrate the Moon Festival, Indian parties for several day for Havaratri, a celebration for the divine feminine Devi.
So, you have lots of good reasons to celebrate September 22nd (1:02PM PDT, 20:02 UTC). Why not at least lift a glass of grog to say goodbye to summer and hello to the beginnings of winter.