Clicked on dock image to open my calendar and got a brand new calendar, with everything set to defaults. None of my sets, categories or other options I have been using for several years and, of course none of my event entries.
What could have caused this, and how do I get back to what I want ?
I back up weekly using Time Machine but can't find my calendar anywhere in TM.

NUD 5.3.1
OSX 10.5.6