Holidays starting 1583

Using this Calendartool, you will be able to calculate the Easter date of each year and all depending Holidays!

Instruction:
Select the year of your choice (between 1563 and 3000; the underlying formula is valid up to 8202!). Start the Calculator!
In the area you will see all the Holidays of the selected year.

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Background
I use a formula out of 1876.
The actual origin of this algorithm appears to be by an anonymous correspondent from New York to »Nature« in 1876. Samuel Butcher, Bishop of Meath, showed that this algorithm followed from Delambre's analytical solutions, and produces the date of Easter for all years in »Butcher's Ecclesiastical Calendar«.
Published also: 1922 in Spencer Jones' »General Astronomy«, p.73f; »The Journal of the British Astronomical Association«, Vol.88, page 91, December 1977, »Practical Astronomy With Your Calculator« by Peter Duffett-Smith, 1979, »Astronomical Formulae for Calculators« by the Belgian Jean Meeus (published 1982 by Willmann-Bell-Verlag, Richmond, Virginia) and »Astronomical Algorithms« (1991) by Jean Meeus.
This algorithm holds for any year in the Gregorian Calendar, which (of course) means years including and after 1583.
More popular is the Easter formula originated 1800 by Carl-Friedrich Gauß (1777-1855).
The Christian tradition celebrates Easter on the Sunday which follows the 1st full moon in Spring. So you have the constants "year" (365,2422 middle sundays) and "moon month" (29,5306 middle sundays).