I have no idea how common the nightmare is. I have never had them. But I did mix up the dates for my exam. My friend called me as I was about to go to the gym

I have no idea how common the nightmare is. I have never had them. But I did mix up the dates for my exam. My friend called me as I was about to go to the gym and asked where I was, with a very concerned voice. It turned out that I was supposed to be at an exam. I rushed home, changed clothes and went like crazy to school. Luckily they let me in as the last one of the day - of course I had not prepared in the slightest - but did absolutely fine :)