Radicale

Radicale is a small but powerful CalDAV (calendars, to-do lists) and CardDAV
(contacts) server, that:

  - Shares calendars and contact lists through CalDAV, CardDAV and HTTP.
  - Supports events, todos, journal entries and business cards.
  - Works out-of-the-box, no complicated setup or configuration required.
  - Can limit access by authentication.
  - Can secure connections with TLS.
  - Works with many CalDAV and CardDAV clients
  - Stores all data on the file system in a simple folder structure.
  - Can be extended with plugins.
  - Is GPLv3-licensed free software.

For the complete documentation, please visit
Radicale v3 Documentation.