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Easter Calculation Rule:
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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 ecclesiastical approximation established by the Council of Nicaea in 325 AD.
The calculator uses Gauss's algorithm for calculating the date of Easter:
a = year mod 19
b = year div 100
c = year mod 100
d = b div 4
e = b mod 4
f = (b + 8) div 25
g = (b - f + 1) div 3
h = (19a + b - d - g + 15) mod 30
i = c div 4
k = c mod 4
l = (32 + 2e + 2i - h - k) mod 7
m = (a + 11h + 22l) div 451
month = (h + l - 7m + 114) div 31
day = ((h + l - 7m + 114) mod 31) + 1
This algorithm computes the date in the Gregorian calendar for years 1583 onward.
Details: The current calculation method was established to standardize the date of Easter across Christian churches. It reconciles the solar year with lunar cycles while maintaining the connection to the Jewish Passover.
Tips: Simply enter any year between 1583 (when the Gregorian calendar was introduced) and 3000. The calculator will determine the date of Easter Sunday for that year.
Q1: Why does Easter's date change every year?
A: Easter is based on a lunisolar calendar (combining moon phases and solar year), causing it to fall on different dates each year.
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 Christians celebrate Easter on the same date?
A: Most Western churches use the Gregorian calendar, while many Orthodox churches use the Julian calendar, often resulting in different dates.
Q5: Why was March 21 chosen as the vernal equinox date?
A: The Council of Nicaea fixed March 21 as the ecclesiastical equinox for calculation purposes, even though the astronomical equinox may vary.