"El dia de demà."

Traducción: El día de mañana.

[miestasmediisto]

does this sentence make sense?

[Oceanotti]

Yes, it does. I is a way of saying "in the future". For instance, you may say: Si fas el curs complet de Duolingo, el dia de demà podràs parlar català to mean “If you take the whole Duolingo course, in the future you will be able to speak Catalan”.