_Slaugh_: Happy Easter,
ZFR!
(Julian Easter?) It's more complicated than that. Part of the discrepancy is due to the differences between Julian and Gregorian calendar, and part due to calculations of the moon phase.
Google can give you all the little details about the calculations. Interesting read if you're into that. The difference is either 0, 1, 4 or 5 weeks. The western Easter is more "astronomically" correct, while the Eastern always comes after Passover, so it's more "religiously" correct.
Having parents from 2 different backgrounds, we generally celebrate both. And yes, Easter eggs are there, so thanks :)