This t-shirt apologizes for you being not really adult like today.
On the black shirt it says in big letters “Sorry I Can’t Adult Today” and that will make it clear that you are not going to be like a boring old person today.
So today is the day to be silly, fun, and irresponsible.
We adults should all have this t-shirt in our closets ready for the day we want to be strange and different then people expect.