CalDav & WebDav
Challenge: allow to sync also between servers.
Webdav is very nice to just publish events. Can be subscribed by anybody (also works with e.g. DavX5 App on Android).
There are several libraries and frameworks that support CalDav:
- Etesync https://www.etesync.com/ - big plus is the encrypted storage, also supported by NLnet, https://github.com/etesync also has web interface
- sabredav - very commonly used in php based services such as nextcloud, GroupOffice, Zarafa https://sabre.io/
- Baikal Server php
- Radicale https://radicale.org/ Python
Edited by Roland Alton