Function SetFileDateTime(FileName : String; NewDateTime : TDateTime): Boolean;
var
FileHandle: Integer;
FileTime: TFileTime;
LFT: TFileTime;
LST: TSystemTime;

begin
Result := False;
Try
DecodeDate(NewDateTime, LST.wYear, LST.wMonth, LST.wDay);
DecodeTime(NewDateTime, LST.wHour, LST.wMinute,
LST.wSecond,LST.wMilliSeconds);
IF SystemTimeToFileTime(LST, LFT) Then
begin
IF LocalFileTimeToFileTime(LFT, FileTime) Then
begin
FileHandle := FileOpen(FileName, fmOpenReadWrite or
fmShareExclusive);
IF SetFileTime(FileHandle, NIL, NIL, @FileTime) Then
Result := True;
end;
end;
Finally
FileClose(FileHandle);
end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
if OpenDialog1.Execute then
begin
if SetFileDateTime(OpenDialog1.Filename,now) then
begin
ShowMessage('Date set to now !');
end;
end;
end;