RealTime is a project mainly written in Java, it's free.
Plugin for bukkit that changes the time to reflect the servers time
RealTime is a plugin that changes the time to reflect the servers time (at least the hours).
For example:
If the real time is 16.40 then the minecraft time would be 16.00
I haven't done a relly thorough testing, but it seems to work.
For (maybe) more information, visit the RealTime site.
It should not work with plugins that changes the time.
As for other plugins that deals with time, I have no idea
if they would would work or not.
None discovered yet.