cyrus-caldav software package provides Cyrus mail system - CalDAV and CardDAV support, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install cyrus-caldav
cyrus-caldav is installed in your system.
Make ensure the cyrus-caldav package were installed using the commands given below,
$ sudo dpkg-query -l | grep cyrus-caldav *
You will get with cyrus-caldav package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | |
| Package | cyrus-caldav |
| Version | 2.5.10-1 |
| Description | Cyrus mail system - CalDAV and CardDAV support |
| Sub Section |