How is the date of Easter calculated?

Easter Sunday is the first Sunday after the first full moon on or after the vernal equinox (around March 21). This rule is not based on astronomical observation but on a set of ecclesiastical tables, which is why the calculated date can differ slightly from the astronomical full moon.

The Anonymous Gregorian Algorithm (Butcher's Method)

The most widely used algorithm for computing Gregorian Easter was published in 1876 in Astronomical Algorithms by Jean Meeus and is often called the Anonymous Gregorian algorithm or Butcher's algorithm. It works for any year in the proleptic Gregorian calendar from 326 AD onward.

Julian vs. Gregorian Easter

Eastern Orthodox churches that follow the Julian calendar celebrate Easter on a different date. The Julian calendar currently runs 13 days behind the Gregorian calendar, so Orthodox Easter typically falls 1 to 5 weeks after Western Easter.

Easter date range

In the Gregorian calendar, Easter can fall no earlier than March 22 and no later than April 25.

Frequently asked questions

Why does Easter move each year?

Easter is a moveable feast; its date changes because it is tied to the lunar calendar (the full moon) and the weekly calendar (Sunday), neither of which aligns exactly with the solar year.

When is Easter 2025?

Easter 2025 falls on April 20 in the Gregorian calendar.

When is Easter 2026?

Easter 2026 falls on April 5 in the Gregorian calendar.