Equinox [from Latin aequinoctium equal nights] The two annual epochs when the sun, in its apparent path around the ecliptic, crosses the celestial equator, occurring about March 2l and September 23, when the days and nights are equal to each other in length. The position of this intersection or node -- the equinoctial point -- on the ecliptic, at the vernal equinox in the northern hemisphere, is called the first degree of Aries in the ecliptic zodiac. But this point shifts continuously, having a retrograde motion around the ecliptic occupying about 25,920 years. This period is very important because every astronomical cycle is indicative of cosmic and human cycles. In accordance with the signs of the zodiac, it is divided into twelve parts, each of 2160 years, called in theosophy the Messianic cycle and marking the coming of a world savior. The recession of the equinoxes from Pisces into Aquarius is stated to occur somewhere about the present age, and to mark a new spiritual dispensation.
In SD 2:330, a cycle is mentioned which is obtained by compounding the processional cycle with the cycle of the apsidal revolution; this, according to figures for apsis and equinox given by modern astronomers, gives a period of about 21,000 years (probably 21,160 years).
The two equinoctial epochs of each year are also highly important as they indicate conditions favorable to certain operations, initiations, and ceremonies. These times were the ones often chosen as being favored for the celebration of the ancient Mysteries and the initiation of candidates; although the two solstices, falling in December and June, are equally important.