All around the world, we are using some conventions to write short dates, and it seem that, despite the variations, none of us is using a nice convention. IMHO, a nice convention must (in addition to code the date):
The US format (mm-dd-yyy) seems to be one of the worth: none of those two simple criteria are reached. The french one (dd/mm/yyyy) is a little better — the order of the elements is logical — but it fails for the second criteria.
The best one seems to be the one nobody use excepted in the computer world: yyyy-mm-dd. That’s the one I’m using for that blog.