The timestamp for my posts (that shown in the page source before it gets java-magic'd into 'in 11 hours') is correct current time for NZ, so I guess the actual message timestamp is generated at the server.
Good detective work! The time descriptions are actually done in the browser. If your timezone is not NZ then they are incorrect.
I have a fix for this ready for the next update. Basically, the time comparison just needed to be timezone-aware.