procedure TForm2.Button1Click(Sender: TObject);
var
  pDateTime:TDateTime;
begin
  FormatSettings.DateSeparator:='-';  //System.SysUtils;
  //System.SysUtils.FormatSettings.TimeSeparator:=':';
  ShowMessage(System.SysUtils.FormatSettings.ShortDateFormat);
  pDateTime:=StrToDateTime('2015-3-28 12:32:1');

  ShowMessage(FormatDateTime('yyyy-mm-dd',pDateTime));

  ShowMessage(FormatDateTime('yyyy-mm-dd hh:nn:ss',pDateTime));

  ShowMessage(FormatFloat('#.000',111113.1415926));
end;