> I think it's related to the fact that if you have been woken up at the same time of day (/morning/night) for a long period of time, you start waking up at this time, even if you alarm clock fails. I once noticed that I regularly woke up 2-5 (aka "a couple of") minutes before I was supposed to. I bet someone has done some serious research on this, but it's one of those things which I can't be bothered to find out.
>
> jul"I'd like to have a poll answering: "Have you ever been able to train yourself to wake up at the right time?""ian

Once I had to get up regularly at 6:45. I would usually try to get at least seven hours sleep. On a weekend it was different as I could sleep as long as I wanted. One Saturday, however, my eyes sprang open and I found myself looking straight at my alarm clock. It read 06:44:53. I had only gone to bed at 1am and my first thought was, "Aw no, gotta go to work." Then I realised it was Saturday and my body just hadn't remembered in time and woken me up ready to got to work.

Bea"Glad he doesn't have to get up QUITE so early these days"sty