Mega Code Archive
Get the week number of a date
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var
FirstWeekDay: Integer = 2;
{ Wochentag, mit dem die Woche beginnt
(siehe Delphi-Wochentage)
2 : Montag (nach DIN 1355) }
FirstWeekDate: Integer = 4;
{ 1 : Beginnt am ersten Januar
4 : Erste-4 Tage-Woche (nach DIN 1355)
7 : Erste volle Woche }
{ liefert das Datum des ersten Tages der Woche }
{ get date of first day of week}
function WeekToDate(AWeek, AYear: Integer): TDateTime;
begin
Result := EncodeDate(AYear, 1, FirstWeekDate);
Result := Result + (AWeek - 1) * 7 - ((DayOfWeek(Result) + (7 - FirstWeekDay)) mod 7);
end;
{ liefert die Wochennummer und das Jahr, zu dem die Woche gehört }
{ get weeknumber and year of the given week number}
procedure DateToWeek(ADate: TDateTime; var AWeek, AYear: Word);
var
Month, Day: Word;
begin
ADate := ADate - ((DayOfWeek(ADate) - FirstWeekDay + 7) mod 7) + 7 - FirstWeekDate;
DecodeDate(ADate, AYear, Month, Day);
AWeek := (Trunc(ADate - EncodeDate(AYear, 1, 1)) div 7) + 1;
end;
{Week to date example}
procedure TForm1.Button1Click(Sender: TObject);
begin
ShowMessage(FormatDateTime('dd.mm.yyyy', WeekToDate(51, 2000)));
end;
{Date to week example}
procedure TForm1.Button2Click(Sender: TObject);
var
week, year: Word;
begin
DateToWeek(now, week, year);
ShowMessage(IntToStr(week));
ShowMessage(IntToStr(year));
end;
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