Calendar widget does not show previous and next month

I am attempting to use the calendar widget; however, when placed in the sidebar widget box, and after updating, the calendar appears with no “previous” or “next” (it appears the link exists because I can roll over my mouse and the cursor turns into a finger). How can I edit the widget to show the previous and next under the calendar?

Also, when I do select the invisible link for previous, the archives for the previous month appears, yet the calendar does not appear in the sidebar.

Can anybody help?

Thank you.