utility creating a dst cache

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