When Is The Autumn Equinox 2024 Date. 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, moving from the northern hemisphere to the southern. Autumn / fall equinox 2024.

The spring or vernal equinox marks the astronomical first day of spring. Autumn / fall equinox 2024.