"Date and Time Settings" GUI in Ubuntu 14.04 is not working?

Solution 1:

That error message is odd. It does not find a key which indeed exists in one of the files belonging to the indicator-datetime package. This command reinstalls the package:

sudo apt-get install --reinstall indicator-datetime

Also, it should be noted that in Ubuntu 14.04 it's unity-control-center to open System Settings from command line, not gnome-control-center. It should be possible to have both the packages installed, but based on my experience there is a risk for conflicts/confusion. So I would recommend that the gnome-control-center package is uninstalled.

Solution 2:

try using this cli

pkill -f indicator-datetime-service

clock will appear directly.

credit : @Sneetsher