Not true. I've always been able to wake up pretty accurately without an alarm clock (not to the minute, but within 30min or so). It's just one of those things some people seem to be able to do, and others can't.

As a result, I've never been particularly dependent on alarm clocks, and use them more as a backup for important events than as my primary method of waking up...

I was first told about this as a kid - the 'trick' was to bang your head (gently) on the pillow for the hour you wanted to wake - so 7 times to wake at 7am.

I tried it all the way through the summer and was amazed - then forgot about it.

When I went travelling I didn't take a watch and remembered the trick (though didn't bother with the head banging) and found I could wake when I wanted pretty accurately.

When I started university I used this method for nearly the whole first term - and never missed a lecture.

If you have been heavily drinking, or have been really run down then yes this won't work, but in normal life it works fine. It helps if the time is part of your routine (waking each day at 7.30 for example) but I've easily got myself to wake at 6 or earlier if I need to.

I find though that if I know i have an alarm then I just fall into a DEEP sleep, and find it much harder to wake. I do find that I feel far less sleepy when I just tell myself to wake.

Anyway, your mileage may vary, but try it - it really does work - remember that farmers etc have been waking before dawn to start work for thousands of years before the advent of clocks.