Hi, we use an shared calendars setup for all (15-20) users in the office. These "shared calendars" are users with calendars, most of them with multiple calendars eg. # user: cal_projects with calendars Project_1, Project_2 etc. The "real login user" are ro or rw proxies (without any own calendars) set via: # calendarserver_manage_principals --add-write-proxy users:user1,user2 users:cal_projects The setup in calendar.app is pretty straight forward: # username: user1 # password: password # server: server.doman.tld # server path: /principals/users/cal_projects/ # port: 8443 # use ssl: yes by setting the server path to # /principals/users/cal_projects/ which calendar.app rewrites to # /principals/__uids__/UUID-OF-THE-SHARED-CALENDAR-USER/ Within Mavericks (10.9.5) this worked very well, even when upgraded to Yosemite (10.10.2) but on every new installed Mac that came with Yosemite these calendars disappear (all at once mostly) after some restarts none deterministic. After that the server path in the config file of that calendar is: # /principals/__uids__/UUID-OF-THE-REAL-LOGIN-USER/ instead of the expected # /principals/__uids__/UUID-OF-THE-SHARED-CALENDAR-USER/ If this happens the respective calendars folder in ~/Library/calendars on the mac is empty (info.plist still there). Calendar.app does not log any useful info. On the server there are those lines in the log when this happens: "REPORT(DAV:principal-search-property-set) /principals/ HTTP/1.1" 200 1362 "-" "Mac+OS+X/10.10.2 (14C109) CalendarAgent/316" i=1 or=1 t=4.2 "PROPPATCH /calendars/__uids__/UUID-OF-THE-SHARED-CALENDAR-USER/calendar/ HTTP/1.1" 401 141 "-" "Mac+OS+X/10.10.2 (14C109) CalendarAgent/316" i=0 or=2 t=17.3 "REPORT(DAV:sync-collection) /calendars/__uids__/UUID-OF-THE-REAL-LOGIN-USER/notification/ HTTP/1.1" 403 208 "-" "Mac+OS+X/10.10.2 (14C109) CalendarAgent/316" i=0 or=1 t=16.1 err=valid-sync-token "REPORT(DAV:sync-collection) /calendars/__uids__/UUID-OF-THE-REAL-LOGIN-USER/inbox/ HTTP/1.1" 403 208 "-" "Mac+OS+X/10.10.2 (14C109) CalendarAgent/316" i=0 or=1 t=26.8 err=valid-sync-token The caldavserver is the version 5.2+dfsg-1 which comes with ubuntu server 14.04 LTS. PostgreSQL is used as data-backend. Account data is stored in /etc/caldavd/accounts.xml because LDAP didn’t work. "ADDRESSBOOK-DATAVERSION";"2" "CALENDAR-DATAVERSION";"6" "VERSION";“28“ Does have anyone have similar problems or even better - any solution to this? Thanks in advance. Frank