How to offer my members the ability to create their own countdown clocks?

Many members on my forums have countdown clocks which are created elsewhere, to help count down the days to their vacation (my site is related to vacations). Often times these countdown clocks have external web urls built into the images, as a form of advertising.

How could I go about hosting my own countdown clock creator for my own users, that they could select from the designs, text to insert onto the clock, and my own website information? Has anyone done this? Having trouble finding via google so hopefully someone here can relate and share some insight.