I'm using 11.10 and haven't ditched Unity, but I believe the calendar in the panel (the upper right of the screen) is part of Gnome. Anyway, I can view the calendar and highlight a specific day but that's it. It's not a shortcut to any calendar that you could do scheduling or anything. Am I missing some functions or is the extent of this calendars interactivity? If the calendar is really just for display, how do I change that to make it actually function with say, Google calendar?
I would suggest installing evolution. You can do this by typing "sudo apt-get install evolution" (Without the "") You can import your Gmail calendar then. Help can be found here
The problem was caused by removing evolution mail client and replacing it with Thunderbird which isn't really "fully functional" yet.