04/05/2026
Catholics and Protestants around the world celebrated Easter today, April 5. Greeks and other Orthodox Christians won't celebrate until next Sunday, April 12. The reason goes back over 400 years to ten days that simply vanished from the calendar.
In October 1582, Pope Gregory XIII ordered a calendar correction so drastic that October 4 was immediately followed by October 15. Ten days were erased overnight. The new Gregorian calendar was designed to fix a growing lag in the older Julian calendar, introduced by Julius Caesar. Catholic and Protestant churches adopted it. Most Orthodox churches did not.
The rule for Easter itself has never changed. Since the Council of Nicaea in 325 AD, all Christians have agreed that Easter falls on the first Sunday after the first full moon on or after the spring equinox. The problem is that the two calendars place the spring equinox on different dates, so the same rule produces two different results.
The Julian calendar now runs 13 days behind the Gregorian. That gap explains why Orthodox Christmas falls on January 7 rather than December 25 for churches like Russia's, which use the old calendar for everything. Greece is a special case: the Greek Orthodox Church uses the reformed Julian calendar for fixed feasts like Christmas, which is why Greeks celebrate Christmas on December 25 alongside Westerners, but still uses the old calendar for Easter.
The Council of Nicaea (325 AD) established that Easter should not coincide with Passover. However, the Orthodox Church does not have a formal "must follow Passover" rule.
The reason Orthodox Easter often follows Passover is a mathematical byproduct. Because the Orthodox Church uses the Julian calendar and a different lunar cycle (the Metonic cycle), their "calculated" Passover usually falls later than the actual Jewish holiday, creating the illusion of a dependency.
Last year, 2025, was a rare exception when both Easters landed on the same date. The next time this happens will be 2028.
Because the Julian calendar gains one day of error every 128 years, the gap between the two calendars will eventually become so large that the Julian "spring" starts after the Gregorian "spring" has already passed its first full moon.