Open Source Calendars

The Calendars we recommend, filtered to Open Source. See all Calendars →

Tuta: Free, Cross-Platform and Zero-Knowledge Calendar

If you decide to self-host EteSync you won't have to pay for the subscription. Tutorial here .

A simple self-hosted CalDAV and CardDAV server for calendars and contacts, written in Python and licensed under GPLv3.

Audited by Cure53 in May 2019.