Mega Code Archive
How to calculate the easter sunday
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Title: How to calculate the easter sunday
Question: A small function that returns the Easter Sunday of a given year.
Answer:
function EasterSunday(aYear: Word): TDateTime;
{ Ash Wednesday := EasterSunday - 46 }
{ Good Friday := EasterSunday - 2 }
{ Ascension Day := EasterSunday + 39 }
{ Whit Monday := EasterSunday + 50 }
{ Corpus Christi := EasterSunday + 60 }
var
R1, R2, R3, R4, R5: Longint;
Easter : TDateTime;
VJ, VM, VD : Word;
begin
R1 := aYear mod 19;
R2 := aYear mod 4;
R3 := aYear mod 7;
R4 := (19 * R1 + 24) mod 30;
R5 := (6 * R4 + 4 * R3 + 2 * R2 + 5) mod 7;
Easter := EncodeDate(aYear, 3, 22);
Easter := Easter + R4 + R5;
DecodeDate(Easter, VJ, VM, VD);
case VD of
26 : Easter := EncodeDate(aYear, 4, 19);
25 : if R1 10 then
Easter := EncodeDate(aYear, 4, 18);
end;
Result:= Easter;
end;
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