vt7: Non-Admin user can't access Calendar Settings...

I created a new non admin user on demo.vtiger.com

I then logged in as that user and went to the Calendar so I could change the Calendar Sharing option from Public to Private.

As a non-admin user the Customise button, and hence the Calendar Settings option, is not visible so you cannot load the configuration popup. And the option to change the Calendar Sharing is not present in the My Preferences->Calendar Settings screen.