Quantos fins de semana já se passaram no ano corrente?

Function WeekNum(const TDT:TDateTime) : Word;
var
Y,M,D:Word;
dtTmp:TDateTime;
begin
DecodeDate(TDT,Y,M,D);
dtTmp := EnCodeDate(Y,1,1);
Result := (Trunc(TDT-dtTmp)+(DayOfWeek(dtTmp)-1)) DIV 7;
if Result = 0 then
begin
Result := 51
end
else
begin
Result := Result-1;
end;
End;