function dn = easter(y) % EASTER Date of Easter. % EASTER(y) is the datenum of Easter in year y. % Ref: Donald Knuth, The Art of Computer Programming, % Fundamental Algorithms, pp. 155-156. % Copyright 2014 Cleve Moler % Copyright 2014 The MathWorks, Inc. % Golden number in 19-year Metonic cycle. g = mod(y,19) + 1; % Century number. c = floor(y/100) + 1; % Corrections for leap years and moon's orbit. x = floor(3*c/4) - 12; z = floor((8*c+5)/25) - 5; % Epact. e = mod(11*g+20+z-x,30); if (e==25 && g>11 || e==24), e = e + 1; end % Full moon. n = 44 - e; if n < 21, n = n + 30; end % Find a Sunday. d = floor(5*y/4) - x - 10; % Easter is a Sunday in March or April. d = n + 7 - mod(d+n,7); dn = datenum(y,3,d);