Since 'How can I make myself get enough sleep?' is on topic, I hope this one is too.
How to know how long I slept last night? or at least if I'm sleeping enough.
I keep track of when I go to bed and when I get up which is an upper bound for the time between falling asleep and waking up. Sometimes I feel like I've just been tossing and turning all night long without actually falling asleep.
- go to bed = physically going onto bed
- get up = physically getting off bed
- fall asleep = unconcious and dreaming
- wake up = concious and thinking