The Dating of Greek Easter—Explained by A Mathematician

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Greek Easter
Easter eggs at market in Athens. Credit: Reinhard Kirchner /Wikimedia Commons/CC BY-SA 3.0

The dating of Greek Easter or Pascha, has bedeviled theologians for centuries. While other Christians in the West are finishing off all their chocolate eggs by now, for some people Easter is happening—seemingly all over again.

By George Sapounidis

Orthodox Christians, in some countries, including Greece and Cyprus, celebrate Easter later than most in the western world.

This may seem either banal or…bizarre. But this isn’t done to confuse everyone. It’s all for mathematical reasons.

Math, did you say? My ears just quivered. If you’re not a numbers guy like me, who has a PhD (Pizza Hut Delivery) in the subject, you could just as well say: Enough already! Why not just pick a day and be done with it!

It’s complicated!

It mostly boils down to the fact that those who adhere to Greek Orthodoxy espouse the calendar devised by Julius Caesar—the Roman general turned dictator—versus the calendar tweaked by the Pope…Gregory, that is, then the leader of the Roman Catholic Church. Hmm…come to think of it, they’re both Roman!

The fundamental problem that anyone making a calendar has to grapple with is the fact that it takes just a shade more than 365 days for Earth to make a full trip around the sun. More precisely, it takes 365.24219 days. Now we’re talking!

So if you construct a calendar with only 365 days, the seasons will fall ever so slowly out of whack with the months. Eventually, Christmas would show up in the middle of summer— chaos!

Enter Caesar! The Julian calendar was a reform of the previous Roman calendar, which was a messy hodgepodge. It took effect on January 1, 46 BC by edict. It was designed with the aid of Greek mathematicians (yes!) and Greek astronomers (yes!) such as Sosigenes of Alexandria.

But things were still a bit out of whack. It had a leap day every four years, which turned out to be an overcorrection. The average year now had 365.25 days in it—just a shade more than 365.24219. By the 1570s, those slight differences had added up. The calendar was now out of sync with the solar year by about ten days.

Enter Pope Gregory! In 1577 he appointed a commission to solve the problem. It took five years, but they finally came up with a fix: First, let’s just eliminate those extra 10 days and get back on schedule. Gone!

Next, let’s tweak the system of leap years. We’ll have leap years every four years except on centennial years that aren’t divisible by 400. So there’s a leap year in 2000, but not in 1900 or 1800 or 1700. In summary, the contemporary Pope decreed (not dictated … big difference) that the ten days following October 4th simply wouldn’t exist. The next day would be…October 15.

In other words, the decree was: “Pfft. Those 10 days? You’ll never miss ‘em.”

Thereafter, a new calendar would come into effect that would better align the months with Earth’s journey around the sun. This would correct a mismatch in the old Roman calendar, first set up by Caesar, that was causing the months to fall steadily out of line with the seasons.

The current Gregorian calendar, with its intricate dance of leap days and leap years, seems utterly banal to those of us in the Western world today. It has a bunch of oddities. Our months are uneven, some 31 days, some 30, plus the monstrosity that is February.

By the way, leap days aren’t the only hassle for timekeepers. We also have leap seconds to contend with. But that’s a story for another day.

Oh yes, the food! Greeks everywhere traditionally eat lamb roasted on a barbecue spit and tsoureki, a sweet Easter bread. They also break their fast with a traditional soup called magiritsa, which is made of lamb, rice and dill before the main feasting begins on Sunday.

And the eggs…hard-boiled yolk-filled oblong spheres painted blood red are used as merciless weapons in a valiant take-no-prisoners round table challenge to see who can out-bludgeon other guest opponents’ eggs. No lame milk chocolate in Orthodoxy!

All this to say Greek Easter can sometimes fall on the same day as Western Easter. This isn’t done on purpose and isn’t done to confuse anyone. But only by pure and unlikely coincidence.
Don’t you love math?

Wishing you Happy Greek Easter!
Καλό Πάσχα! Καλή Ανάσταση!

George Sapounidis is a Greek-Canadian mathematician who is also a musician, bridging Greek and many other cultures in his work.

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