That is the perfect solution! I remember clicking on the "Calendars" button to see what that would do when they first redesigned iCal to Calendar in Lion. It was useless back then as I recall, just allowing the selection of "calendars" (eg, "Work", "Personal", etc.) but did not have the small calendars at the bottom.

So I never rechecked for that. But the ML version has been upgraded to restore the "clickable small calendars" function. Yay!

Now my next issue, which is with the Calendar widget in the Dashboard -- with ML they put a bug or feature in whereby dates on the calendar are not clickable, hugely reducing the usefulness of the widget. You can change months with the arrow keys, but apparently cannot change the date at all. Unless there is some hidden keystroke/mouse combination that does it.

Hugely annoying because you cannot quickly "check your calendar". You first have to open up the Calendar program, then navigate.

I have reported this bug to Apple Feedback.