I must have been very asleep. That's all I can think of.
Last night, I woke up as usual on a weekday. I pressed the button to turn off my clock radio. I got myself out of bed and took a shower. I returned to bed to rest a few minutes.
It was then that I realized it was 12:45 am. My alarm doesn't go off until 5:30! I was befuddled as to why I would have gotten up when I did, when my pager buzzed its little reminder buzz. My pager had gone off at 12:30, but in my stupor I thought it was my clock radio!
I felt rather ridiculous, especially since I was now awake enough to start the day! I refused to get up, though, and soon enough went back to sleep. The only side effect was that my hair dried kinda funny since I was sleeping on it wet.