is it Tuesday or Wednesday

All semester, I have been confusing my M/W and T/TH classes. Not the classes themselves. I arrive in the correct locations at the correct times, but I invert the days. As a result, it was Tuesday all day yesterday, as far as I was concerned, even in the last week of the semester. Is it that I have always taught Photography on T/Th? And Monday throws me off? Is it that I normally teach my digital class on M/W? And both those trends hold such strong positions in my psyche, that they can deny reality? I don't know. Next semester, all my classes are T/Th. I think I will redo my fall schedule so they fall where they are supposed to.