Here is an example of widget to do a count-down to a particular event.
In this example, I just use icalbuddy to see how much time I have before my next meeting (using icalBuddy).
But this should basically work for any kind of event/ (like the time to the star of the world cup/...)
To limit cpu usage the time to the next update is automatically adjusted to not run the script if no update is expected. (so I update every minutes the last hour, otherwise every hour the last day and otherwise every 24h.
Do not hesitate to tell me for which reason you use a countdown. Can be fun