I "accidentally" clicked on the calendar toolbar button and now the calendar is covering my grid.
I got this new button in the Grid:

How do I remove it? Clicking on the calendar toolbar button doesn't toggle it off; right-clicking doesn't give me the option to remove it; dragging it off also doesn't work...

EDIT: after a lot of experimenting did I finally remove it (not sure exactly what I did). When I now click on the calendar button nothing happens. It may be a bug because the Calendar is actually in a Pane below the Grid mentioned above....