Taking a blind guess because there's so little information here. Maybe this is related to the recent troubles with Google authentication.
https://bugzilla.gnome.org/show_bug.cgi?id=771547 Are you using Unity or GNOME or some other desktop? Was your calendar in sync with Google Calendar before? As a workaround, please try restarting your computer. ** Bug watch added: GNOME Bug Tracker #771547 https://bugzilla.gnome.org/show_bug.cgi?id=771547 -- You received this bug notification because you are a member of Ubuntu Desktop Bugs, which is subscribed to gnome-calendar in Ubuntu. https://bugs.launchpad.net/bugs/1633053 Title: gnome-calendar 3.20.4 inoperable after update on 13 October 2016 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gnome-calendar/+bug/1633053/+subscriptions -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs