Act like it's Thursday.
e.g. When your boss says, "Where the hell are you? It's time for the meeting I've been reminding you about all week." You say, "Wait, that's not until tomorrow." And he says, "We're all waiting for you over in 3-C right now, numbnuts." And you're like, "Wait, it's Friday?" And he's says, "Nevermind about the meeting. You're fired." And you're like all, "Right on. Now I'll never be confused about what day of the week it is. Because it's all-Friday, all-the-time for me from now on."
The irony: you were never really confused about what day of the week it was in the first place.