Is there any sort of instruction on adding calendar controls to Zen-cart web pages?

I am trying to create a pop-up calendar control for a date field on a report. I found several other admin pages that use a calendar pop-up using spiffycal v 2.1, and attempted to copy the code for their calendar code into another form.

At this point, the control is displayed on the screen; however, it is not functional. Clicking on the icon that should actually show the calendar box does nothing, in both IE and Firefox. (In Internet Explorer, it generates a javascript error:
Error: 'document.all[...].style' is null or not an object

I figure I've forgotten to include some file or set some variable but can't figure out what.

Or, is spiffycal the best option for calendar controls?