I'm not familiar with this. I think that while XMPP supports offline/invisible status, the Cisco Jabber client doesn't itself. It sounds like whatever software you're using is looking for a time frame for that status to be held for. My guess is it either goes back to a calendaring integration or available outside of that time? Seems like an odd feature to have in the client but ... my guess anyway for whatever it is that you're using.
