You searched for: “autumnal equinoxes
autumnal equinox (s) (noun), autumnal equinoxes (pl)
The intersection of the ecliptic and the celestial equator that the sun passes each year: The autumnal equinox makes day and night of equal lengths.

The autumnal equinox takes place about September 23 in the northern hemisphere and on March 21 in the southern hemisphere.

This entry is located in the following unit: Astronomy and related astronomical terms (page 4)