How is Autumn Equinox calculated?

This event is based on the astronomical moment when the Sun crosses the celestial equator heading southward each year.

When is Autumn Equinox 2026?

Wednesday, 23 September 2026

Autumn Equinox marks the astronomical point when the Sun crosses the celestial equator heading southward, signalling the beginning of autumn in the Northern Hemisphere and spring in the Southern Hemisphere.

Also known as

Autumnal Equinox
Southward Equinox

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Frequently asked questions

When is Autumn Equinox 2026?: Autumn Equinox 2026 is on Wednesday, 23 September 2026.
What day of the week is Autumn Equinox 2026?: It falls on Wednesday.
How is Autumn Equinox calculated?: This event is based on the astronomical moment when the Sun crosses the celestial equator heading southward each year.