I have a problem with DirectPathloader

when executing following code I will get a

ORA-01841 (year < -4713 or zero or >+9999)
Row =0, Column = 1

error in the sourcecode line of 'Ldr.Load(Row);'

Code
/Fill the array 
    for i := 0 to .... do         
    begin
      resarray[i].dts:=formatdatetime('dd.mm.yyyy hh:nn:ss',dt); //String
...
    end;
...
    ldr.DateFormat:='DD.MM.YYYY HH24:MI:SS';
    ldr.Column[1].DataSize:=21;
    ldr.Column[1].DateFormat:='DD.MM.YYYY HH24:MI:SS';


  for i := 0 to length(Resarray) - 1 do
  begin
...
    ldr.Column[1].SetData(Row, @Resarray[i].dts[1], length(Resarray[i].dts));
...

    Inc(Row);
    // We have filled the array, or we are at the end of the file: load it
    if (Row = Ldr.MaxRows) or (i = length(Resarray) - 1) then
    begin
      try
        Ldr.Load(Row);
      except
        on E:EOracleError do
        begin
          showmessage(E.Message + #13#10#13#10 +
...
The date format of the loader is set correct and also the dateformat in the field. The resarray[i].dts contains strings like '01.07.2012 00:00:00'. There are no constraints in the table.

What could be the problem?