[sm=sleeping.gif]
I think it has to do with your REM's and what stage of sleep you are in...
I had to do 12 hour graveyard shifts last year - and I would get home at 11:30 in the morning,
immediately go to sleep - wake up at around 5:30 in the afternoon jumping out of bed
and thinking I was late for work... when i didnt have to be in till 11pm that evening.

I guess it can be nice too when you think you have school / work and then *ding* it hits you -
it's Saturday LOL.