"Sharing calendars and contacts between users, on the same system or across systems"

TC SHARING is working on sharing calendars anc contacts between users on a CalDAV and/or CardDAV system by rationalizing and extending current informal specifications.

TC FSC (Federated Shared Calendars) is working on sharing calendars and hopefully contacts across calendaring system, e.g being able to share between multiple systems such as iCloud, Google Calendar, Yahoo!, AOL, and so forth.