"The date of the dance is the seventh of October."
Translation:La fecha del baile es el siete de octubre.
I was always taught that the cardinal numbers were used for dates, except for the first, which had to be "el primero." That was a long time ago, and I recently saw Dúo use "el uno de" for "the first" (in one of the new sentences), so I'm assuming things have changed. In a way though, I'm kind of glad to see that the ordinal number wasn't accepted for you. (Sorry!)