Keeper.sh now imports any calendar from its iCal subscription link. Give the calendar a name, paste the link, and its events start arriving. Added calendars are listed on the integrations page and can be removed at any time.
Some links are not public. When a link asks for credentials, Keeper.sh prompts for a username and password instead of failing, so a work calendar behind basic authentication connects the same way a public one does.
When an import fails, the error names the cause: the link was unreachable, the credentials were refused, or the file was not a calendar. Keeper.sh then refetches each link on a schedule, so what it holds stays in step with the original.
What each calendar service asks for covers connecting every kind of calendar, links included.