The script for the widget comes from the handy script library that is "Google Gadgets." I expect that those gadgets will disappear sooner or later, and I know I could use my own (limited) javascript skills to write a similar sort of gadget of my own... but I've been using this particular gadget for my classes for at least four or five years now, so I will be sorry to see it go. I have to admit that I also like seeing the clock tick down to the end of the semester!
Here is the script; you can see the variables that are easy to adjust - month, day, year, and so on:
Here is the script; you can see the variables that are easy to adjust - month, day, year, and so on: