Autumn Equinox 2024 Time. 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,. The autumn equinox is the moment when the sun passes the earth's equator and for one nanosecond the earth is neither.
The autumn or fall equinox signals the end of summer on the astronomical calendar. When is the autumn equinox in 2024?