Contributor: MARK LUSSIER
{>> Has anyone an algorithm to determine moveable feasts - such as Easter -> which is calculated by the year? by any other method?
Popular question this past 2 days. Here is our kcEaster function from our KingCalendar product. Just pass it the year and it will
return a TDateTime for Easter. Enjoy the code, it was a fun to write
function kcEaster( nYear: Integer ): TDateTime;
var
nMonth, nDay, nMoon, nEpact, nSunday, nGold, nCent, nCorx, nCorz: Integer;
begin
{ The Golden Number of the year in the 19 year Metonic Cycle }
nGold := ( ( nYear mod 19 ) + 1 );
{ Calculate the Century }
nCent := ( ( nYear div 100 ) + 1 );
{ No. of Years in which leap year was dropped in order to keep in step
with the sun }
nCorx := ( ( 3 * nCent ) div 4 - 12 );
{ Special Correction to Syncronize Easter with the moon's orbit }
nCorz := ( ( 8 * nCent + 5 ) div 25 - 5 );
{ Find Sunday }
nSunday := ( ( 5 * nYear ) div 4 - nCorx - 10 );
{ Set Epact (specifies occurance of full moon }
nEpact := ( ( 11 * nGold + 20 + nCorz - nCorx ) mod 30 );
if ( nEpact < 0 ) then nEpact := nEpact + 30; if ( ( nEpact = 25 ) and ( nGold> 11 ) ) or ( nEpact = 24 ) then
nEpact := nEpact + 1;
{ Find Full Moon }
nMoon := 44 - nEpact;
if ( nMoon < 21 ) then nMoon := nMoon + 30; { Advance to Sunday } nMoon := ( nMoon + 7 - ( ( nSunday + nMoon ) mod 7 ) ); if ( nMoon> 31 ) then
begin
nMonth := 4;
nDay := ( nMoon - 31 );
end
else
begin
nMonth := 3;
nDay := nMoon;
end;
Result := EncodeDate( nYear, nMonth, nDay );
end;