As before, the method is from Butcher's Ecclesiastical Calendar (1876). I present it in the form given in Peter Duffett-Smith's Practical Astronomy With Your Calculator (Cambridge 1981, the 1988 version is still available from Amazon, et al). And once again, I'd like to add that Mr. Duffett-Smith's books are among the most fun and interesting math books you'll ever find!
I'm no JavaScript wiz, but I did test it in both MSIE7 and Chrome. However, as always, this code is presented “as-is” and without warranty or implied fitness; use at your own risk.
function easterForYear (year) {
var a = year % 19;
var b = Math.floor(year / 100);
var c = year % 100;
var d = Math.floor(b / 4);
var e = b % 4;
var f = Math.floor((b + 8) / 25);
var g = Math.floor((b - f + 1) / 3);
var h = (19 * a + b - d - g + 15) % 30;
var i = Math.floor(c / 4);
var k = c % 4;
var l = (32 + 2 * e + 2 * i - h - k) % 7;
var m = Math.floor((a + 11 * h + 22 * l) / 451);
var n0 = (h + l + 7 * m + 114)
var n = Math.floor(n0 / 31) - 1;
var p = n0 % 31 + 1;
var date = new Date(year,n,p);
return date;
}
