agenda.app software package provides Calendar manager for GNUstep, 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 agenda.app
agenda.app is installed in your system.
Make ensure the agenda.app package were installed using the commands given below,
$ sudo dpkg-query -l | grep agenda.app *
You will get with agenda.app package name, version, architecture and description in a table
| Distro | Ubuntu 16 04 lts xenial xerus |
| Section | Miscellaneous |
| Package | agenda.app |
| Version | 0.42.2-1ubuntu3 |
| Description | Calendar manager for GNUstep |
| Sub Section | Misc |