Sunday, April 5, 2009

Why aren't Passover and Easter always the same time?

If the Last Supper was a Passover Seder (which is debatable) why aren't the two holidays always the same time of year?

It's because of the different calendars -- the Jewish lunar calendar and the complex, albeit mixed solar lunar calendar, way Easter's date is calculated.

Passover is always the 14th day of Nisan on the Jewish calendar, a fixed date.

Easter is always the 1st Sunday following the 1st full moon of Spring, at least for Western Christians.

Eastern Orthodox Christians and Eastern Rite Catholics following the Julian Calendar will never celebrate Easter before Passover.


Mockingbird said...

I like your post: Brief, to the point, and technically accurate.

However, to say that Passover is Nisan 14 , while technically true, but can be misleading in a modern context. When a modern almanac or calendar designates a day as "Passover", it means not the Passover strictly so-called (Nisan 14) but the 1st day of Unleavened Bread (Nisan 15). If a calendar shows a day marked "Passover begins at sunset", then that day is, indeed, Nisan 14, but "Passover" (meaning the Feast of Unleavened Bread) does not begin until sunset, after which it is no longer Nisan 14, but Nisan 15.

Comparing the fixed lunar date of the feast of Unleavened Bread with the variable solar date of Easter is to some extent an apples-and-oranges comparison. On the lunar side of the Gregorian (or Julian) calendar, Easter is always the 3rd Sunday in its lunar month, so while it is not a fixed date in the Christian lunar calendar, it is fixed to a specific week, like American Thanksgiving. That is, the Gregorian (or Julian) calendar computes a lunar month of 29 or 30 days, and sets Easter to the 3rd Sunday, which is necessarily the Sunday falling in the week of the 15th to the 21st inclusive of the lunar month.

If Christians used the same lunar calendar as Jews, Easter would always be the Sunday falling in the Jewish week of Unleavened Bread, but since the 3rd century Christians have done their own lunar computations, so they don't always agree on the age of the moon--today, Sunday April 5th, 2009, is the 9th day of the lunar month by the Western Christian count, but the 11th by the Jewish count--or on which lunar month is the one for the spring festival. Three years out of every 19 Jewish Nisan is a moon later than the Christian Easter-moon, due to a small underlying summerward drift in the Rabbinic calendar's implicit solar year.

Stating that Christians following the Julian calendar "will never celebrate Easter before Passover" is technically true, but again it can be misunderstood. Indeed, the Eastern Christians themselves have misunderstood it. Since at least the 12th century Eastern Orthodox canonists have taught that Easter must never coincide with Nisan 15 of the Rabbinic calendar. But this "Zonaras proviso" is in fact spurious. There is no such rule in the Julian lunar calendar. Julian Easter is always after Rabbinic Nisan 15 simply because the errors in the Julian calendar have become fairly large. The Julian solar calendar is 13 days behind the Gregorian and roughly 10 days behind the Rabbinic, and the Julian lunar calendar is 4-5 days behind the Rabbinic and Gregorian. In the Julian lunar calendar, today is only the 5th day of the lunar month, not the 9th as in the Gregorian or the 11th as in the Rabbinic. So of course the 15th of a Julian lunar month will always occur after the 15th of a Rabbinic lunar month.

James C Morton said...

Excellent point and yes, really it is 15 Nissan

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