The saturday after hard pAArtying on friday night. Due to lack of sleep, being hungover, etc., the whole day is basically a waste of tiredness, nausea, and sometimes regret over the previous night's activities.
Does not necessarily have to only be saturday.
I had such a good time friday night, at least from what I can remember lol, that I spent the rest of the weekend in a saturdaze.
Our friday night parties have become so awesome that I've had a long string of saturdaze.