Today Is The Thirty Firsth

Heard in the car yesterday:

Zach: Dad, what's the date-th?

Eric: What? Do you mean the date?

Zach: No, I mean the date-th. You know, like what number is it today with "th" at the end?

Eric: Oh, it's the 30th. But it's not always "th" at the end. Sometimes it's "st" or "rd" or "nd".