I know that in Mail, Inbox (2) means two unread messages. Under My Calendars I see Calendar (2). What does the (2) mean here?

It means you have some unread items on your Calendar. Maybe appointments or something??

I still don't get it. All my appointments are entered by me, so how can they be "unread". I do not use Exchange, so there are no corporate invitations to join a meeting.
In any case, how do I find an appointment that is unread? Is there a Search function?

The calender(2) indicates a duplicate calender name. Renaming the calender will remove this.

Best Regards,

Sorry, but you are incorrect. I have only one Calendar. When I click on the Properties for that Calendar I see two Check boxes labeled:
Show number of unread items.
Show total number of items.
When I click on Show total I get (660). When I click on Show unread I get (2).
So Shawn76 is correct. The (2) is the number of unread items. Which brings us back to my original question, "What is an unread calendar item?" And how do I find the two that are unread?
Cheers