alarm-clock-applet software package provides alarm clock panel indicator, you can install in your Ubuntu 16.04 LTS (Xenial Xerus) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install alarm-clock-applet
alarm-clock-applet is installed in your system.
Make ensure the alarm-clock-applet package were installed using the commands given below,
$ sudo dpkg-query -l | grep alarm-clock-applet *
You will get with alarm-clock-applet package name, version, architecture and description in a table
| Distro | Ubuntu 16 04 lts xenial xerus |
| Section | GNOME |
| Package | alarm-clock-applet |
| Version | 0.3.4-1 |
| Description | alarm clock panel indicator |
| Sub Section | GNOME |