General   (General discussion, talk about anything.)

I find I have always been able to estimate the time to within 10 minutes. Within five, if we exclude the immediate proximity to waking up, or falling asleep.

In fact, tom, I get the problem which you describe if I DO use an alarm clock.

Much better if I just decide when I want to wake.

99.9% of the time, I will succeed.

Of course, late nights, being sleep deprived, drinking etc interferes with the ability, and can result in oversleeping.