Question: Dear Webmaster: Unlike Christmas, Easter comes on a different date every year. How is date derived? Much appreciated!
Response: Easter is a feast day - one of the few that the reformed Church chose to continue to celebrate after the split with Rome (although the trend is now to incorporate rather more such feasts). It is supposed to duplicate and memorialize the day of our Lord's resurrection. Problem is, of course, that reconstructing the exact day is very difficult and still open to question. This is because the Passover was not held on a particular day of our calendar (our calendar wasn't even invented until the sixth century A.D.), and, in the way it was applied by our Lord's time was - to make a long story short - a complicated business. Hoehner's Chronological Aspects of the Life of Christ does a good job explaining the problems and coming up with a likely solution. But since the exact year of the crucifixion is debated (I believe for reasons set out in part 5 of the Satanic Rebellion series that it was 33 A.D.), the exact day of the year remains open to question, even if we could agree on the precise Jewish application of the Law on these matters in the early first century (cf. Ex.12:1-3) - since the Jewish calendar is lunar, based on twelve 30 day months and using intercalation to fill up the extra days (and the specifics of this are not set forth in the Bible) it would be difficult to come up with the precise day even if the exact year were known and accepted. Add to this the fact that Easter must come on the first day of the week, Sunday, and we have a guarantee that it would not always be on the same day, even if our chronological knowledge were perfect.
All this is by way of introduction to show that in the days of the early Church when much of what we now know was not known the problem of coming up with the exact day of that Sunday that followed that Passover would have been quite a challenge, and so what we have is a system built on approximation and perpetuated by tradition (of which there are several: "Greek Easter" for example, a system to derive the date of celebration in the Eastern church, is different from the Rome derived system). About all they knew for sure when these systems were established (it is similar for Christmas, by the way - it was not always celebrated on the 25th of December in all places), was that Passover was always on the tenth of the first Jewish month and that came in the spring, the limits of which are determined by its full moon with extremes of March 21st and April 25th. So the differences between the two systems, if one may speak in generalities here, are due to which Jewish paschal cycle is preferred, with the Alexandrian [eastern] computation being on a 19 year cycle, and the Roman [western] computation based on an 84 year cycle. Other factors were thrown in over time [how late and how early were acceptable, either of which could result in a change if the maximum/minimum dates were exceeded].
There are a number of websites out there that have formulae for figuring this out [not posted here as the addresses keep changing]. The main point that I would like to bring up here is that Jesus is our Passover (1Cor.5:7), Jesus is the resurrection and the life (Jn.11:25). The point is not to worship Him on any one day or any particular time, but to worship Him on all days and at all times, and not to worship the day we have chosen to represent His work (Gal.4:10).
For more on the true events of that day, please see the following link:
The Resurrection (in BB 4A)
Yours in Christ,