This happened to me last week in a midterm! I actually sat there and hand-wrote "hte" on the exam. Good thing I caught it.
Temporal Warp/Involuntary Pulsing - this is one I forgot to mention earlier, but when I get totally immersed in an activity, I get totally immersed. So much, in fact,that hours will pass that have only felt like a few minutes to me. Some video games/art projects can do this, but the vast majority of the time it's happened, I've been reading. Oddly, reading while in Temporal Warp Mode also produces some interesting side effects: either people will forget I'm even there, or they'll not notice I'm reading - convenient for when you haven't noticed that class started twenty minutes ago, but not so much when you're reading an Inquisitor fight scene and people keep wanting to talk at me. Not to me, at me. It's really weird.