By Kate Quiñones
CNA Staff, Apr 17, 2025 / 09:00 am
While Easter dates usually differ between Eastern and Western Christians, this year both Easter celebrations land on the same day — a coincidence that could be an opportunity for progress in ecumenical dialogue.
This year’s Easter falls in the 1,700th anniversary year of the Council of Nicaea — the first ecumenical council that was held in the fourth century. Most known for defending the divinity of Christ against the heresy of Arianism, the council also established a universal formula for calculating the date of Easter.
Nicaea decreed that Easter should be celebrated on the first Sunday after the first full moon following the spring equinox. The Julian calendar, which was the standard at the time, had a fixed date for the spring equinox. The fixed Easter date, based on the Julian calendar, was gradually implemented.
Centuries after the council, Western churches switched to the Gregorian calendar due to inaccuracies in the Julian calendar, while the Eastern Church has continued to use the Julian calendar for religious feast days. Both East and West follow the council, but they have different starting points and therefore different Easter dates.
Why has the Easter date been different?
In 46 B.C., Julius Caesar established the Julian calendar. While similar to the now-standard Gregorian calendar, the Julian calendar had its flaws.
Minute inaccuracies in the Julian calendar caused worlds of confusion centuries afterward, affecting agriculture and planting, shipping navigation, and even the celebration of holy days.
While a year is colloquially known to be 365 days, it takes the earth precisely 365.24219 days to travel around the sun. The Julian calendar intended to account for that extra bit of time by establishing a leap year every four years.
