>>2284851It's not quite that esoteric. It's the first Sunday following the first full moon after March 21st (the vernal equinox).
The only time it gets any weirder than that is if you're determining it according to the Orthodox tradition (as opposed to the Catholic or Protestant traditions), which uses March 21st in the Julian calendar (rather than the Gregorian calendar everyone normally uses) as the date of the vernal equinox.
