Calendars are not visible in the iCal sidebar I recently upgraded my MacBook Pro to macOS Sierra and since then I have noticed that none of my calendars appear in the sidebar space to the left of the ical window.

Can anyone help me to get these back please?

All my calendar events are visible in the actual calendar, and my iCloud account is active and visible when I log in. Its just that the side bar is completely blank.
I had the same problem and after a quick Google search found my solution: I quit and restarted Calendar, clicked the Calendars button and the calendars list reappeared.