Ruby code to compute the date of Easter Sunday for given year.

easter.rb

# Helper for computing the date of Easter Sunday.

require 'date'

class Date
  def self.easter_sunday(year)
    a = year % 19
    b, c = year.divmod 100
    d, e = b.divmod 4
    g = (8 * b + 13) / 25
    h = (19 * a + b - d - g + 15) % 30
    i, k = c.divmod 4
    l = (32 + 2 * e + 2 * i - h - k) % 7
    m = (a + 11 * h + 22 * l) / 451
    month, day = (h + l - 7 * m + 114).divmod 31
    new(year, month, day + 1)
  end
end

# EOF #