This program demonstrates how to determine the easter date for a given year.

It's quite complex:


function GetEaster(Year: Integer): TDate;
var
  y, m, d: Word;
  G, I, J, C, H, L: Integer;
  E: TDate;
begin
  G := Year mod 19;
  C := year div 100;
  H := (C - C div 4 - (8*C+13) div 25 + 19*G + 15) mod 30;
  I := H - (H div 28)*(1 - (H div 28)*(29 div (H + 1))*((21 - G) div 11));
  J := (Year + Year div 4 + I + 2 - C + C div 4) mod 7;
  L := I - J;
  m := 3 + (L + 40) div 44;
  d := L + 28 - 31*(m div 4);
  y := Year;
  // E is the date of the full moon
  E := EncodeDate(y, m, d);
  // find next sunday
  while DayOfWeek(E) > 1 do
    E := E + 1;
  Result := E;
end;

{
Usage
var EasterDate: TDateTime;
...
EasterDate := GetEaster(2002);
}


//* it may work under Delphi v1.x and v2.x as well. i tested it with Delphi 6 Enterprise and it worked fine. *//