When Is The Autumnal Equinox 2024. In 2024, that will occur on sunday, sept. The autumnal equinox (as well as spring equinox) is the moment when neither of the earth’s hemispheres is inclined towards or away from the sun.

Find out more about equinoxes and solstices. In 2024, the autumnal (fall) equinox arrives on sunday, september 22, marking the official first day of fall.