easter-sunday.js

// golfed-down JS code to calculate the date of easter sunday for a given year
// based on the Gaussian Easter Formula (https://en.wikipedia.org/wiki/Computus)
function(y){var a=y%19,b=(19*a+24)%30,d=b+(2*(y%4)+4*(y%7)+6*b+5)%7;d-=d^35&(d^34|b^28|a<11)?0:7;y=new Date(y,2,22+d);return y}

function(
  y // year input, later used as date object / return value
){
  // calculate moon parameter
  var a = y % 19,
  // get the seed for the first full moon in spring
      b = (19 * a + 24) % 30,
  // day correction for sunday
      d = b + (2 * (y % 4) + 4 * (y % 7) + 6 * b + 5) % 7;
  // exceptions: d must not be 35 and not 34 if b is also 28 and a < 11
  d -= d ^ 35 & (d ^ 34 | b ^ 28 | a < 11) ? 0 : 7;
  // create date object; use the interesting property that you can set dates beyond the
  y = new Date(y, 2, 22 + d);
  // return easter date
  return y
}