Autumn Equinox 2024. Autumn equinox 2024 (beginning of astronomical autumn) on the day of the autumn (september) equinox, the sun, moving along the ecliptic, crosses the celestial equator,. Autumn equinox 2024 (beginning of astronomical autumn) on the day of the autumn (september) equinox, the sun, moving along the ecliptic, crosses the celestial equator,.

An equinox is one of two days in the year when the sun crosses the equator and day and night become equal in length. The 2024 fall equinox—also called the autumn equinox—takes place on sunday, september 22, 2024.