I have

Last friday I had to make an appointment to make some weird experiment for my thermodynamics class. I had to do the experiment with other three people and they asked me to make the appointment. I went to the mechanical engineering department where I found a list with the possible times I could choose for the appointment, so, I write (or I thought I did) my name down in front of "December 5, 2 to 4pm". I sent an e-mail to all my mates I was doing the experiment with telling them the date.

Today, we went to the laboratory to do the experiment and there was another group to do the same experiment, which was impossible because no more than one group could be working on that at the same time. We were very confused, so, one of my group mates went to the department to check the list of appointments, he came back:
"Today is... tuesday, right?" he asked me
"yep, tuesday" I answered
"Ok... you made the appointment for tomorrow, 2 to 4pm.. those things happen"

What?!?!? I couldn't believe it, I was sure I made the appointment for today so I went to the department to check and, yeah... I made the appointment for tomorrow, not today Now, I think I'm going a little crazy

So, have you ever happened something like this? Or have you had another kind of experience that made you thought "I'm losing my mind"?