Need help about join date??

I just create my own forum couple days ago, but there seems to be one little problem. Members join date doesn´t seems to be working. Here you can see how it is: http://kaasu.forumn.org/tiedotteet-f1/infoa-keskustelupalstasta-t3.htm.
In my own informations, under the pic, join date should be in a place where is text Liittynyt: (Joined) and a letters after that mean dd/mm/yyyy. In case that someone here doesn´t speak finnish. Evidently this isn´t the way it should be. How can I fix this or can I