fruux is a calendar service from Germany. Their CalDAV server is open source.
European alternatives to Google Calendar
Google Calendar is a calendar service from the US-American company Google.
This pages lists European Google Calendar alternatives from companies based in a member state of the European Union (EU) or the European Free Trade Association (EFTA).
Proton Calendar is a calendar service with a strong focus on privacy based in Switzerland. Proton Calendar uses zero-knowledge encryption, which means that the company can not read the content of your calendar even if they are stored on their servers.
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