I was taught to use cardinal numbers when you are using dates in a sentence, with the exception of when the day precedes the month.
For example: The event will take place on July 4. OR... The event will take place on the 4th of July.
So... is the following sentence wrong?
The event will take place on July 4th?
To eliminate confusion, I usually change it to July 4, 2010, but I really want to know what is acceptable, and what is not.