EQUINOX Either of the two times each year when the sun crosses the equator and day and night are of equal length everywhere. During the spring (vernal) equinox (about March 21), it is said that an egg will stand on its small end. Although some people have reported success, it is not known whether such results were due to the equinox or to the peculiarities of that particular egg. Others insist that some eggs will stand on their small ends at any time of the year.