1. What is the Easter Calculation?

The Meeus/Jones/Butcher algorithm is a method for calculating the date of Easter Sunday in the Gregorian calendar. It's more compact than other methods while maintaining accuracy for all years in the Gregorian calendar (from 1583 onward).

2. How Does the Calculator Work?

The calculator uses the Meeus/Jones/Butcher algorithm:

Where:

• \( a = year \mod 19 \)
• \( b = \lfloor year/100 \rfloor \)
• \( c = year \mod 100 \)
• \( d = \lfloor b/4 \rfloor \)
• And several other intermediate calculations

Explanation: The algorithm computes Easter as the first Sunday after the first full moon occurring on or after the vernal equinox.

3. Importance of Easter Calculation

Details: Accurate Easter calculation is important for Christian liturgical calendars and for determining dates of related movable feasts like Ash Wednesday, Pentecost, etc.

4. Using the Calculator

Tips: Enter any year between 1583 (first year of Gregorian calendar) and 4099. The calculator will determine the date of Easter Sunday for that year.

5. Frequently Asked Questions (FAQ)

Q1: Why does Easter's date change every year?
A: Easter is based on a lunisolar calendar, tied to both the solar year and lunar phases, specifically the first Sunday after the first full moon following the vernal equinox.

Q2: What's the earliest possible date for Easter?
A: March 22 (last occurred in 1818, will next occur in 2285).

Q3: What's the latest possible date for Easter?
A: April 25 (last occurred in 1943, will next occur in 2038).

Q4: Does this work for Eastern Orthodox Easter?
A: No, this calculates Western Easter. Orthodox Easter uses the Julian calendar and different calculations.

Q5: Why does the algorithm have a 1583-4099 limit?
A: 1583 was the first year of the Gregorian calendar. The 4099 limit is arbitrary but covers most practical needs.