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# johndyer/easter.js

Last active April 9, 2024 16:28
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Calculate Easter in JavaScript
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 /** * Calculates Easter in the Gregorian/Western (Catholic and Protestant) calendar * based on the algorithm by Oudin (1940) from http://www.tondering.dk/claus/cal/easter.php * @returns {array} [int month, int day] */ function getEaster(year) { var f = Math.floor, // Golden Number - 1 G = year % 19, C = f(year / 100), // related to Epact H = (C - f(C / 4) - f((8 * C + 13)/25) + 19 * G + 15) % 30, // number of days from 21 March to the Paschal full moon I = H - f(H/28) * (1 - f(29/(H + 1)) * f((21-G)/11)), // weekday for the Paschal full moon J = (year + f(year / 4) + I + 2 - C + f(C / 4)) % 7, // number of days from 21 March to the Sunday on or before the Paschal full moon L = I - J, month = 3 + f((L + 40)/44), day = L + 28 - 31 * f(month / 4); return [month,day]; }

### CraigDavison commented Jan 20, 2023

When using this, I was passing the year in from an form input and it seems as though, only odd numbered years, returned the correct date (being Easter Sunday). The answer was to ensure the value passed in was an integer so added a line at the top of the function.

`year = parseInt(year)`