The feeling you get when you fall asleep in daylight and wake up in the complete dark of night. Usually accompanied by slight dizziness and inability to balance yourself properly.
Friend: Hey, why're you walking in zig-zags?
Me: Damn it! Can't you see I'm bed lagged?
A bedlag (not unlike jetlag) is a funny feeling associated to the subjectiveperception of time while asleep.
Someone who is experiencing a bedlag is usually thinking 'God, it's already morning in the country i left my alarm clock in!'