Easter Calculation Formula

Easter Calculation Formula:

\[ p = year \mod 19 \] \[ q = \left\lfloor\frac{year}{100}\right\rfloor \] \[ easter\_day = \text{complex formula} \]

Easter Date:

p (year mod 19):

q (floor(year/100)):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is the Easter Calculation Formula?

The Easter Calculation Formula is a mathematical algorithm to determine the date of Easter Sunday for any given year. It's based on the computus, a calculation that has been used since the Middle Ages to determine the date of the Christian holiday.

2. How Does the Calculator Work?

The calculator uses the Gauss algorithm for Easter calculation:

\[ p = year \mod 19 \] \[ q = \left\lfloor\frac{year}{100}\right\rfloor \] \[ \text{... complex intermediate calculations ...} \] \[ \text{Final date determination} \]

Where:

\( year \) — The input year (1583-9999)
\( p \) — Year modulo 19 (Metonic cycle position)
\( q \) — Century component
Other intermediate variables calculate the exact date

Explanation: The algorithm accounts for the lunar cycle and solar year differences to determine the first Sunday after the first full moon following the vernal equinox.

3. Importance of Easter Calculation

Details: Accurate Easter date calculation is crucial for Christian liturgical calendars and determines the dates of many related movable feasts like Ash Wednesday, Pentecost, and others.

4. Using the Calculator

Tips: Enter any year between 1583 (first year of Gregorian calendar) and 9999. The calculator will show the date of Easter Sunday for that year along with intermediate values.

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 cycles, unlike fixed-date holidays.

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

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

Q4: Why does the algorithm start with year mod 19?
A: This represents the Metonic cycle, a 19-year period after which moon phases repeat on the same dates.

Q5: Are there different calculations for Orthodox Easter?
A: Yes, Orthodox churches often use the Julian calendar for calculation, resulting in different dates.