I am a firm believer that we must have a magical internal time-keeping system, that is always running, without our awareness.
For as long as I can remember, and far too many times to count, I've woken up exactly one minute before my alarm went off. I know this happens to a lot of people. Why is it??
Do you think it happens more when we look at the clock right before we close our eyes to fall asleep, and then something inside of us says, ok, let's keep track and wake up exactly one minute before the alarm so we don't have to hear that nasty thing?
And it has never mattered what time I go to sleep, what time I wake up, how many hours of sleep I've had, etc. etc. I've never been able to figure out why it happens.