The Radicale Project is a complete CalDAV calendar server solution.
It can store multiple calendars.

Calendars are available for both local and remote access, possibly
limited through authentication policies. They can be viewed and
edited by calendar clients on mobile phones or computers.  Technical
Description

Radicale aims to be a light solution, easy to use, easy to install,
easy to configure. As a consequence, it requires few software
dependencies and is pre-configured to work out-of-the-box.