The Actionsupport DOM events include "onchange", "onclick", "ondblclick", "onfocus", "onkeydown", "onkeyup", "onmousedown", "onmousemove" and so on and so on, and these are all in lowercase, despite the occasional new Javascript convention to camelCase them.
That easily cost me half an hour of visualforce debugging, and not for the first time!
Now, as a quick test to make sure you were paying attention, why won't my daysbox element rerender in this code snippet?? Use your eyes, and your minds..
