Tomorrowday generally refers to the hours between 8am until the general hour that the sun starts to set (otherwise known as "tomorrow evening")
Friend1: Oh no! It's 3 a.m. too late! Did I make you lose your time?
Friend2: No, please don't worry.
Friend2: Well, I'd better go to sleep now. History's homework is for tomorrowday (10 a.m.), and I didn't finish it.
Friend1: Sorry. I really made you lose your time.