One of the meanings of the word число is date in the sense of the first of the month, the second, and so forth. Probably the most common usage is this:

Since число is a neuter noun, and since words like first and second are adjectives in Russian, the adjective must show up in the neuter singular form when answering the question:

An English speaker will never say “Today is the first date,” but Russians sometimes do include the word число in the response. Of course, when translating that response into English you must leave the word ‘date’ out:

It is also possible to ask about future and past dates:

Back when I first started studying Russian, it irritated me that no textbook ever gave a complete set of examples of how to say today's date. Instead they gave a general instruction with a few examples and just assumed the student could get the rest right. That's awful teaching methodology. A non-Russian student has to deal with the quirks of Russian stress, plus he has to correctly generate the neuter form of the adjective. That seems very easy after you have worked on Russian for several years, but at first it's tricky. Rejoice, therefore, ye Russian novices: here I present a complete table of all 31 dates marked for stress so you may double check your work.

Notice particularly that третье ‘third’ has a soft-sign as the next-to-the-last letter, not an o. Notice also that одиннадцатое has not just one н but two in a row as the fourth and fifth letters.