Ecclesiastical full moon March 21 (the ecclesiastical fixed date for the Equinox), Easter was the following day—Sunday March 22—the earliest date possible. It will not fall on this date again until 2285, a span of 467 years. In 1943 a full moon fell on Saturday March 20. As this was before March 21, the next full moon, which fell on Sunday April 18, determined the date of Easter—the following Sunday, April 25. It will not fall on this date again until 2038, a span of 95 years. For a detailed discussion of the paschal computations, see Computus. By the middle of the third
Equinox zero. Its latitude will not be exactly zero, since Earth is not exactly in the plane of the ecliptic. Its declination will not be exactly zero either. (The ecliptic is defined by the barycenter of Earth and the Moon combined.) The modern definition of equinox is the instants when the Sun's apparent geocentric longitude is 0° (northward equinox) or 180° (southward equinox). See the adjacent diagram. Because of the precession of the Earth's axis, the position of the vernal point on the celestial sphere changes over time, and the equatorial and the ecliptic coordinate systems change accordingly. Thus when specifying