Yes, you can rename calendars, and all users in your tenant should be able to see the changes once a sync is performed. Please do the following to rename your calendars and sync this change to your users:
- Click the calendar you would like to edit in the Calendar pane.
- Click NEXT until you get to Step 3: Specify calendar options.
- Change the name of your calendar in the box under Provide Calendar Name.
- Click SAVE.
- Run a manual sync with Update Cache checked.