Grammar Goody # whatever (I can't keep track anymore): Ordinals in dates

I am really perplexed by the sudden appearance of this typical mistake: the use of ordinals in dates. This is what I mean:

The tragedy occurred on September 11th, 2001.


That, I'm afraid, is incorrect. Sure, it's correct in spoken English, but not in written English. (The ordinal, by the way, is that "th" after the number--or it could be "rd" with the number 3 or "st" with the number 1.

The only correct way to write out a date is like this:

The tragedy occurred on September 11, 2001.

So, please drop the ordinals! They're just plain wrong.