Autumnal Equinox September 2024. It is this day on which day the ancient greek. Autumnal equinox — is an astronomical phenomenon, when the sun in its visible motion along the ecliptic crosses the celestial equator.

It’s time to bust out your favorite seaters, gather autumnal foliage for home. September 22nd is when the autumnal equinox begins and the night gains ground over the day as the position of the sun and moon change.