Change date format in Word 2000

[s97]

When I type a letter, I always type the date under my address in the
format:

11th October 2006

But when I have typed it, it comes out in the format:

11th October 11-10-2006

with the "th" part of the date as a superscript.

This happens 99% of the time, and I have to waste time fiddling about
trying to change it to the format I want. Strangely, very occasionally
it uses the date I have actually typed in.

Is there some way to set the format of the date in Word? I believe this
can be done in Excel, so it must somehow be possible in Word.

Thanks for any advice.

s97