I've been using a external 21.5' monitor for my laptop of 12.1' monitor, and moved my top panel to the right and add a new panel to the bottom edge of the screen. A screenshot of the right part of my desktop:
As you see, The window of the calender is out of the screen. The alt+left mouse button did not work. How do you move the calender window?
update: I managed to come up with a solution to get the window or panel of cal in the screen. Just remove the panel of clock and re-add it. But unfortunately, the preferences are lost. You have to reset the preferences, such as locations...
but after re-adding 2 locations, the window of cal panel was just shown as the same of the previous screenshot before.