There's a "family calendar" at Casa Mens which is shared on several devices: we're reminded when the next dinner invitation is and when our friends celebrate their birthday. This calendar was on a Gmail account because Google has a service that just works.
The operative word is was on a Gmail account.
For years, literally, I've been searching for a suitable replacement, and the data-privacy "issues" have kicked me into action: future data will be better hidden.
To cut a short story even shorter, within four hours I had
- set up a server here with TLS,
- installed MySQL,
- installed and configured Baïkal,
- used iCal to export CalDAV from Gmail to a local file,
- imported said file to Baïkal using iCal,
- and re-configured all iDevices to use our new CalDAV server.
Android's support for CalDAV and CardDAV is pretty abysmal (understandibly), and so is its address book. I'm experimenting with aCAL (which certainly takes first prize for having the worst design I've ever come accross in an app) and CalDAV-Sync.