- Occasion when day and night are of equal length - Short horse mounts ox? It happens twice a year... - When night and day are of equal length - The time when the sun enters one of the equinoctial
points, that is, about March 21 and September 22. See Autumnal equinox,
Vernal equinox, under Autumnal and Vernal. - Equinoctial wind or storm.