The most famous ancient remnant of autumnal equinox celebrations has to be the ancient Mayan monument of Kukulcan, in the complex of Chich'en Itza. Much is made of ancient architecture that coordinates with the rise and set of the sun (Alexander the Great famously made an entire city that was oriented around the line of the sun on his birthday), but the Mayans made their own version of equinox-worship deeply creepy.

Kukulcan is dedicated to the feathered serpent god Quetzalcoatl, and its pyramid steps are precisely oriented so that, twice a year on the spring and autumn equinoxes, a shadow "flows" down the stairs to connect a tail statue at the top and a feathered snake-head statue at the bottom. It's a renowned phenomenon and a tourist attraction, but for the Mayans it was a deadly serious serious: it likely represented the two times in a solar year that Quetzalcoatl visited the temple in person. It's not known exactly what the rites of the autumnal equinox with the shadowy serpent might have been, but the god's equinox shadow points towards the area's sacred sinkhole filled with natural water, so perhaps Quetzalcoatl descended from the heavens to hydrate twice a year.

We use the word "Adonis" today to refer to any kind of beautiful man, but in ancient Mediterranean civilizations, it harkened back to the pairing of the goddess Aphrodite and her paramour Adonis, who was doomed to die while still young and gorgeous and was transformed into flowers. The two of them had their own cults, and ancient Cyprus was a particular site of worship for them. When it came to the autumnal equinox, the women of Cyprus did a bit of gardening for Adonis.

For the ancient Cypriots, Adonis didn't just represent beauty; he was also a god of fertility and life itself, and needed rites to guarantee health and good harvests. In a ritual that was deeply similar to the worship of the god Tammuz among ancient Syrians, the women treated Adonis as "dead" before the equinox began, mourned him with loud weeping, then buried or hid pots filled with earth and plants (like fennel, barley, and wheat) known as the "gardens of Adonis." When they later dug them up, the seeds would be sprouting, marking Adonis's rebirth and the success of life over death. (In Sicily, this ritual still happens, but is tied to Good Friday, instead of an ancient good-looking god.)

The Greeks had their own ideas about how necessary women were to the autumnal season. The Thesmophoria and Stenia festivals, while not always directly tied to the equinox, were part of ancient Greece's method of welcoming in the harvest months and thanking the gods who'd given men all that glorious food.

The essence of the two festivals was a kind of topsy-turvy gender reversal in which women took control and escaped their normal domestic roles. Only married women were allowed to participate, and it got weird pretty quickly. They were festivals in devotion to Demeter, the god of harvest and the natural world, and her love for her daughter, Persephone. The Stenia, or purifying period before the Thesmophoria, heralded a kind of preparatory chaos: women gathered together to trade aiskhrologia, ritual rude remarks and insults, in the hope of making Demeter laugh. Priestesses would also go poke around in chasms, where they'd left pork carcasses to rot for several months, and leave them on altars for farmers to sow alongside new crops. Same.

The Thesmophoria involved all kinds of role reversals, including women electing female officials, but mostly it required married women to escape domestic duties for three days, leave their homes and go live in the woods as a group, whipping each other with bark, trading insults, going on marches with torches at night, and probably having a great time.

When the French Revolution hit and an entire way of life was swept away, from feudalism to the royals, the revolutionaries also decided to reinvent the calendar, to make it less religious and old-fashioned, and more in line with the secular, modern France of their dreams. Out went the saints' days, references to pagan gods, and anything that sounded like a reference to royalty. They chose the autumn equinox as the mark of New Year for its symbolism (and because the equinox of 1792 was also the first day of the new republic), and rearranged the 12 months that followed to closely mirror the pre-established seasons.

The calendar makes for poetic, if slightly bonkers, reading, likely because the committee that put it together included a gardener and a poet. The months were Vendemiaire (grape harvest), Brumaire (foggy), Frimaire (cold), Nivose (snowy), Pluviose (rainy), Ventose (windy), Germinal (germination), Floreal (flowering), Prairial (meadow), Messidor (harvest), Thermidor (heat), and Fructidor (fruiting), after which the autumn equinox happened and the cycle began again. (An unappreciative British observer renamed them "Wheezy, Sneezy and Freezy; Slippy, Drippy and Nippy; Showery, Flowery and Bowery; Hoppy, Croppy, and Poppy".) Much to the relief of the rest of Europe, which was still on the Gregorian calendar, this only lasted from 1793 to 1805, when Napoleon eliminated it.

On the autumn equinox in 1938, at precisely 12 noon, a giant 800-pound cylinder was lowered into the ground at the World's Fair in Flushing Meadows, New York. It was the Westinghouse Time Capsule, and remains in the "Immortal Well" to this day; it's only meant to be opened in 6939, 5000 years from its internment.

What's inside? A collection of 20th century paraphernalia meant to convey to the people of the future what living in the 1930s was like. The list is an extensive one: Camel cigarettes, a fountain pen, asbestos cloth, a huge sample book of fabrics, seeds, messages from "notable men" (sorry, no women) like Albert Einstein, and film clips of everything from Jesse Owens' Olympic wins to a Florida fashion show. A lot of the items are now completely obsolete. It's not clear whether people in 6939 will get the message, or know that they should open it on the autumn equinox themselves — though it would make for some poetic symmetry if they did.