Ubuntu – Missing date & time applet from top Unity panel

If you're running Unity, not Gnome Shell, my guess is that indicator-datetime isn't running. Try running /usr/lib/indicator-datetime/indicator-datetime-service from a terminal window. Hopefully that'll fix things. If not, please edit your question to include the exact error message(s) you received.

To launch a terminal, hit Ctrl+Alt+T. You can also type this command to get a list of indicators that are currently running:

ps -ef | grep [i]ndicator

Try reseting its configuration

dconf reset -f /com/canonical/indicator/datetime/ 

If it didn't show up try kill it, it should restart

pkill -f datetime

For similar cases, better to explain how you may get it:

1. Check if it is running, if yes then possibly a configuration problem

   $ ps ax | grep -i indicator-datetime
    2863 ?        Ssl    0:00 /usr/lib/x86_64-linux-gnu/indicator-datetime/indicator-datetime-service
    4043 pts/0    S+     0:00 grep -i indicator-datetime
   

2. Check for where is its configuration. Look for /etc/ or dconf in /usr/share/glib-2.0/schemas/. List package files using:

   $ dpkg -L indicator-datetime
   [...]
   /etc/xdg/autostart/indicator-datetime.desktop
   /usr
   /usr/share
   /usr/share/glib-2.0
   /usr/share/glib-2.0/schemas
   /usr/share/glib-2.0/schemas/com.canonical.indicator.datetime.gschema.xml
   [...]
   

3. Locate its dconf path:

   $ grep path /usr/share/glib-2.0/schemas/com.canonical.indicator.datetime.gschema.xml
       <schema id="com.canonical.indicator.datetime" path="/com/canonical/indicator/datetime/" gettext-domain="indicator-datetime">