When I upgraded to Ubuntu 12.04, one of the first things I did was to click the Date & Time Settings > Clock tab and set the clock to show seconds as well as the Month and Date. Then I installed gnome-tweak-tool and ran that. I noticed that the clock settings were all set to off underthe tweak tool. I have tried to toggle those and they have no effect on the clock in the tray. So I tried to go back to Date & Time > Clock under System Settings, but the Clock tab is now missing.

Can someone tell me how to eithet get tweak tool to work correctly or at least get the Clock tab back? Thanks.