(1) Install or re-install indicator-datetime:
$ sudo apt-get install indicator-datetime
(2) Re-configure the date/time:
$ sudo dpkg-reconfigure -f noninteractive tzdata
(3) Restart unity service:
sudo killall unity-panel-service
(4) Launch “System Setting” > “Time & Date” > “Clock” Tab.
Check “Show a clock in the menu bar”.
After upgrade or install Ubuntu 13.10, the system time seems to be changed to UTC time.
How to change back to local time?
(1) Click on the time at menu bar to set to correct local time.
(2) Set parameter UTC=no at /etc/default/rcS
$ sudo vi /etc/default/rcS
UTC=no
(3) Reboot machine
$ sudo reboot
#– Add following lines into 50-unity-greeter.conf –#
$ sudo vi /etc/lightdm/lightdm.conf.d/50-unity-greeter.conf
allow-guest=false
greeter-show-remote-login=false
#– reboot machine –#
$ sudo reboot