$ sudo apt-get update
$ sudo apt-get install awn-applet-cairo-clock 

awn-applet-cairo-clock is installed in your system.

Make ensure the awn-applet-cairo-clock package were installed using the commands given below,

$ sudo dpkg-query -l | grep awn-applet-cairo-clock *

You will get with awn-applet-cairo-clock package name, version, architecture and description in a table

awn-applet-cairo-clock package basic information: