Equinoxes, the two annually recurring times at which the sun arrives at the Equinoctial Points (q.v.), viz., 21st March and 22nd September, called respectively the vernal and the autumnal equinoxes in the northern hemisphere, but vice versa in the southern; at these times the sun is directly over the equator, and day and night is then of equal length over the whole globe.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Equinoctial Points * Equites, The