Code:
function GetFileLastAccessTime(
  sFileName : string ) : TDateTime;
var
  ffd : TWin32FindData;
  dft : DWord;
  lft : TFileTime;
  h   : THandle;
begin
  h := Windows.FindFirstFile(
         PChar(sFileName), ffd);
  if(INVALID_HANDLE_VALUE <> h)then
  begin
    Windows.FindClose( h );
    FileTimeToLocalFileTime(
      ffd.ftLastAccessTime, lft );
    FileTimeToDosDateTime(lft,
    LongRec(dft).Hi, LongRec(dft).Lo);
    Result := FileDateToDateTime(dft);
  end;
end;

MessageDlg(
    'c:config.sys was last accessed on ' +
    DateTimeToStr( 
      GetFileLastAccessTime( 'c:config.sys' ) ),
    mtInformation, [mbOk], 0 );