2. Worse when it's after bedtime.
3. Not wise to be unable to fall asleep when waiting for houseguests to come home ("OMG did they miss last train?")
4. It gets bright too damned early.
5. The alarm clock does not care that you're tired and will go off at its normal time.
6. Work also will start at it's normal time, and today is the WORST DAY OF THE LAST 20 to take off to sleep.