The Spring Equinox is the date upon which the liturgical calendar of the Church is based. All of the moveable Feasts of the Church depend on Easter, which falls on the first Sunday after the first full moon after the Spring Equinox.
On the day of an equinox, day and night are of approximately equal duration. After the equinox, day becomes longer than night; light overpowers darkness and nature is awakened.
The full moon is the opposition of the Sun and Moon, astronomically. In ancient tradition, the Planetary Genius of the Sun is Mikael, which became the Christian Saint Michael. This opposition of the Night Star to the Day Star is the battle of Mikael with Lucifer, Typhon-Set with Osiris, Ormuzd with Ahriman.
Easter commemorates the victory of Mikael on the first day governed by the Sun (Sunday), after the mythical battle…
(Adapted from “In the Shadow of the Cathedrals” by Robert Ambelain, Trans. P. Vaughn.)
“In the afternoon of the spring equinox, weigh and measure your prima material. Purify it, separate the elements, and then aid and promote the action of Nature. Consecrate the generating crucible, awaken the god hidden in matter, with prudence and according to the traditional rites and age-old experience. Free the mineral spirit enclosed in your prima material, wash and purify it, vivify it using the Fire Principle, and for that still follow Mother Nature.”
- Pseudo-dedication of Jehan de Chelles to the Virgin Mary.
(Source: Ambelain, Robert. "In the Shadow of the Cathedrals.")