Hubzilla and Nextcloud both offer features for managing contacts and calendars, but they cater to different needs:
Hubzilla focuses on social networking and doesn’t have built-in calendar or contact management features. However, some Hubzilla servers offer integrations with third-party calendar and contact apps.
Nextcloud excels at personal cloud storage, including contacts and calendars. You can store your contact information and calendar events on your own server, giving you complete control and privacy over your data.
NO
Hubzilla has a build calendar and has a contact management, also a personal cloud storage and gives you complete control and privacy over your data.