In the simplest life hack we'll ever provide, we are proud to inform you that today, it is Friday. As the blog Science of Us pointed out, yesterday was Thursday. More helpfully, they explained why it's so hard to mentally keep track of the days during a short workweek, such as the one we're currently wrapping up.
Your perception of time is malleable, and heavily influenced by things such as the five-day work-week, social psychologist Dr Anne Wilson told Science of Us. To your brain, the concept of "Monday" or "Wednesday" isn't just a certain tick out of five, but a bundle of associated emotions and thoughts such as "medium-tired" or "the day I usually feel like pad thai". When you have an unusual day, it messes up those associations and throws off your brain's internal calendar for a while.
So forgetting the day of the week is normal and cool, and it doesn't mean you're the gibbering idiot from this Space Ghost Coast to Coast clip.
To remedy the problem, Science of Us recommends you look at a calendar.