Javascript calendar date picker

This is my first stab at a light-weight popup date picker in Javascript with calendar view. It should be easy to add to an existing form control and low impact to the formatting of the page. To satisfy these two requirements the script should be self-contained in a single js file with a single css file for styles. Triggering the script should be event-driven so it can be bound to a form element inline or with another library like jQuery.

See an example

Next step: port to FBJS to implement in my latest Facebook project.