Easter Date Calculator

Easter Calculation:

Easter = first Sunday after first full moon after March 21

Easter Date:

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1. How Is The Easter Date Calculated?

Easter Sunday is determined as the first Sunday after the first full moon occurring on or after the vernal equinox (March 21). This calculation follows the Gregorian calendar rules established in 1582.

2. The Calculation Method

The calculator uses Gauss's algorithm for calculating the date of Easter:

\[ \begin{align*} a &= year \mod 19 \\ b &= \lfloor year/100 \rfloor \\ c &= year \mod 100 \\ d &= \lfloor b/4 \rfloor \\ e &= b \mod 4 \\ f &= \lfloor (b + 8)/25 \rfloor \\ g &= \lfloor (b - f + 1)/3 \rfloor \\ h &= (19a + b - d - g + 15) \mod 30 \\ i &= \lfloor c/4 \rfloor \\ k &= c \mod 4 \\ l &= (32 + 2e + 2i - h - k) \mod 7 \\ m &= \lfloor (a + 11h + 22l)/451 \rfloor \\ month &= \lfloor (h + l - 7m + 114)/31 \rfloor \\ day &= ((h + l - 7m + 114) \mod 31) + 1 \\ \end{align*} \]

This algorithm computes the month and day of Easter Sunday for any given year in the Gregorian calendar.

3. Historical Background

Details: The current method of calculating Easter was established by the First Council of Nicaea in 325 AD and refined with the Gregorian calendar reform in 1582. It ensures Easter falls between March 22 and April 25.

4. Using the Calculator

Tips: Simply enter any year between 1583 (when the Gregorian calendar was adopted) and 3000, then click Calculate to see 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 the lunar cycle (full moon) rather than the solar cycle, so its date varies annually.

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: Do all Christian churches celebrate Easter on the same date?
A: Most Western churches use the Gregorian calendar calculation, while many Orthodox churches use the Julian calendar.

Q5: Why was March 21 chosen as the vernal equinox date?
A: This was the approximate date of the equinox in 325 AD when the calculation method was established.