When Western and Orthodox Easter fall on the same day

Why they meet, and why they will stop

Both churches keep the same rule, the first Sunday after the Paschal full moon (Wikipedia, “Date of Easter”), but apply it in different calendars and to different reckoned moons. The Julian calendar now runs 13 days behind the Gregorian, so its March 21 is the Gregorian April 3. From 1900 to 2100 the Julian full moon falls 4 to 5 days after the Gregorian one in 148 years and 34 to 35 days after it in the other 53. When the two moons are days apart and no Sunday comes between them, both reckonings choose the same Sunday.

Computed year by year from 1583 to 9999, the last year in which the two fall on the same day is 2698. The distance between the calendars grows by 3 days every 400 years. Western Easter is never later than April 25 and Orthodox Easter never earlier than Julian March 22, so once the calendars are more than 34 days apart, from the year 4900, the earliest Orthodox Easter comes after the latest Western one and a shared date is impossible. All of this is arithmetic under the present rules, which the churches could change (Wikipedia, “Date of Easter”).

Every year from 1900 to 2100 has its own page of Easter dates; the Easter date calculator shows both dates for any year from 1583. Observance varies by church and by country. Whether a feast is a day off work is a matter of each country’s law: Holidays lists each country’s public holidays, off the open Nager.Date database.