The Dating of Greek Easter—Explained by A Mathematician

Easter eggs astatine a marketplace successful Athens. Credit: Reinhard Kirchner /Wikimedia Commons/CC BY-SA 3.0

The dating of Greek Easter oregon Pascha has bedeviled theologians for centuries. While different Christians successful the West are finishing disconnected each their cocoa eggs, for immoderate people Easter is happening—seemingly each implicit again.

By George Sapounidis

Orthodox Christians, successful immoderate countries, including Greece and Cyprus, observe Easter aboriginal than astir successful the Western world.

This whitethorn look either banal or…bizarre. But this isn’t done to confuse everyone. It’s each for mathematical reasons.

Math, did you say? My ears conscionable quivered. If you’re not a numbers feline similar me, who has a PhD (Pizza Hut Delivery) successful the subject, you could conscionable arsenic good say: Enough already! Why not conscionable prime a time and beryllium done with it!

The dating of Greek Easter is complicated

It mostly boils down to the information that those who adhere to Greek Orthodoxy espouse the calendar devised by Julius Caesar—the Roman wide turned dictator—versus the calendar tweaked by the Pope…Gregory, that is, past the person of the Roman Catholic Church. Hmm…come to deliberation of it, they’re some Roman!

The cardinal occupation that anyone making a calendar has to grapple with is the information that it takes conscionable a shadiness much than 365 days for Earth to marque a afloat travel astir the sun. More precisely, it takes 365.24219 days. Now we’re talking!

So if you conception a calendar with lone 365 days, the seasons volition autumn ever truthful dilatory retired of whack with the months. Eventually, Christmas would amusement up successful the mediate of summer— chaos!

Enter Caesar! The Julian calendar was a betterment of the erstwhile Roman calendar, which was a messy hodgepodge. It took effect connected January 1, 46 BC by edict. It was designed with the assistance of Greek mathematicians (yes!) and Greek astronomers (yes!) specified arsenic Sosigenes of Alexandria.

But things were inactive a spot retired of whack. It had a leap time each 4 years, which turned retired to beryllium an overcorrection. The mean twelvemonth present had 365.25 days successful it—just a shadiness much than 365.24219. By the 1570s, those flimsy differences had added up. The calendar was present retired of sync with the star twelvemonth by astir 10 days.

Enter Pope Gregory! In 1577 helium appointed a committee to lick the problem. It took 5 years, but they yet came up with a fix: First, let’s conscionable destruct those other 10 days and get backmost connected schedule. Gone!

Next, let’s tweak the strategy of leap years. We’ll person leap years each 4 years but connected centennial years that aren’t divisible by 400. So there’s a leap twelvemonth successful 2000, but not successful 1900 oregon 1800 oregon 1700. In summary, the modern Pope decreed (not dictated … large difference) that the 10 days pursuing October 4th simply wouldn’t exist. The adjacent time would be…October 15.

In different words, the decree was: “Pfft. Those 10 days? You’ll ne'er miss ‘em.”

Thereafter, a caller calendar would travel into effect that would amended align the months with Earth’s travel astir the sun. This would close a mismatch successful the aged Roman calendar, archetypal acceptable up by Caesar, that was causing the months to autumn steadily retired of enactment with the seasons.

The existent Gregorian calendar, with its intricate creation of leap days and leap years, seems utterly banal to those of america successful the Western satellite today. It has a clump of oddities. Our months are uneven, immoderate 31 days, immoderate 30, positive the monstrosity that is February.

By the way, leap days aren’t the lone hassle for timekeepers. We besides person leap seconds to contend with. But that’s a communicative for different day.

Oh yes, the food! Greeks everyplace traditionally devour lamb roasted connected a barbecue spit and tsoureki, a saccharine Easter bread. They besides interruption their accelerated with a accepted crockery called magiritsa, which is made of lamb, atom and dill earlier the main feasting begins connected Sunday.

And the eggs…hard-boiled yolk-filled oblong spheres painted humor red are utilized arsenic merciless weapons successful a valiant take-no-prisoners circular array situation to spot who tin out-bludgeon different impermanent opponents’ eggs. No lame beverage cocoa successful Orthodoxy!

All this to accidental Greek Easter tin sometimes autumn connected the aforesaid time arsenic Western Easter. This isn’t done connected intent and isn’t done to confuse anyone. But lone by axenic and improbable coincidence.Don’t you emotion math?

George Sapounidis is simply a Greek-Canadian mathematician who is besides a musician, bridging Greek and galore different cultures successful his work.