But you can install which ever locale you desire (from those that are available).

I suggest that you consult the Debian Wiki entry on Locale - TKL v12.x is based on Debian Squeeze (aka 6).

If you need more info and/or specific instructions I'm sure that google will help you out.

It'd be great if you can post back some specific instructions once you have it worked out. That will save others from having to search the info out (as you'll have to).