utility creating a dst cache

[Chuck Soper]

Hello,
I'm writing a utility that uses the tz database. One of the features 
is to quickly (via a cache saved to disk) display daylight saving 
times for a given year and tz location. If the tz package is updated 
then I will need to re-create my dst cache.

Is there a way to programmatically determine if the tz package has 
been updated since the last time I ran my utility? Is there a way to 
determine if a specific zoneinfo file has been updated?
Thanks, Chuck