the problem is you can't shift all people clock because you are having a nap so would be either you wait or you can't shift the clock ahead 
it's a multiplayer game unfortunately 
What you need is a dreamland then, to keep players busy during sleep.
About abuse, someone, please describe what type of abuse you expect. All I imagine at the moment is littering (tents kept in game while owners are away) and lag (too many tents aggregated). In that regard, you could:
- not allow tents inside cities (I'll always mention the obvious
)
- make tents constantly wear off (quality reduce, up to 0=ruined) when setup. They can be greased or fixed or whatever, either when set up or not, so that people need to visit them regularly. Abandoned tents would then disappear automatically when they become garbage.
- make groups of tents attract mobs (for example 0% chances with 1 tent, 5% chances every hour when 2 tents close, etc.). The tents could be destroyable by mobs, or simply suffer automatic fast decay whenever combat happens close-by.
Another thing that could be of interest is to make larger tents impossible to be carried by 1 person alone (a matter of volume), and to require a group to be raised.
Oh! And make them burn when setup too close to a campfire.
