I was the only person online at the time, and I've tried sleeping in the main world and never noticed it skipping to daytime. :-/
There's no reason the server should let me sleep but not you? :/ Maybe you should backup and reinstall your client?
Has he tried turning it off and on again?
There's a reason it's a cliché. :P
Because everyone does it?
Because computers have state, but most programmers don't really understand this and only deal with what they want to happen, which often results in things getting into a state that is only solvable by discarding and starting again.
So then why wouldn't just closing the program fix it?
Why doesn't blinking stop you from being tired?
Because sometimes I have to poop?
Server was playing up earlier and being very laggy/inconsistent, and now it seems down altogether.
Dynamic map is online though, so it might just be Minecraft itself needs a kick.
(just letting you know - no plans to use it again tonight, so no worries if you're busy with other things)