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procedure TForm1.BitBtn1Click(Sender: TObject);
begin
  if FileExists('bilder\save.bocky') then
   begin
    DOSDatum:=FileAge(Dateiname);
    WinDatum:=FileDateToDateTime(DOSDatum);

     if Now - WinDatum =  30 then
      begin
       {usw.}					

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if Now - WinDatum =  30 then					

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if Now - WinDatum =  30 then					

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var
  Datum1, Datum2: TDateTime;
begin
  if (Datum1 - Datum2) >= 30 then
  begin
    foo(...);
  end;
end;					

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uses
  DateUtils;					

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procedure MyProcedure;
var
  FileDate: Integer;
  DateTime: TDateTime;
begin

  if FileExists(FileName) then
  begin
    FileDate := FileAge(FileName);
    DateTime := FileDateToDateTime(FileDate);
    if DaysBetween(Now, DateTime) > 30 then
    begin
      // Datei ist älter als 30 Tage
    end;
  end;

end;					

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procedure TForm1.BitBtn1Click(Sender: TObject);
begin
  if FileExists('bilder\save.bocky') then
   begin
    DOSDatum:=FileAge('bilder\save.bocky');
     if Now - Windatum >= 30 then
      begin
       DeleteFile('bilder\save.bocky');
      end
   end;					

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WinDatum:=FileDateToDateTime(DOSDatum);