Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

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
     if SetFileDateTime(OpenDialog1.FileName, now) then
       ShowMessage('Date set to now !');
 end;