The personal web site of Rick Koshko (married name Rick Wiegmann Koshko).
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Enter a year in the form below to calculate the Easter date for that year. You can select the Julian or Gregorian calendar. Be careful using the Gregorian calendar for past centuries. That calendar wasn't adopted everywhere at the same time.
If you want to use the formula yourself, go ahead and look at the source code. The formula was published in Astronomical Algorithms by Jean Meeus who attributes it to earlier publications as far back as 1876.
By and large, Christian churches that observe Easter do so on the first Sunday following the first full moon after the vernal equinox. They calculate the vernal equinox by methods slightly less accurate than today's astronomers use, so occasionally the Easter date will seem to violate the rule.