There are some great libraries both for iOS and Android to display the current time given a timezone identifier and there is a free database available for those (http://en.wikipedia.org/wiki/Tz_database). Figuring out what timezones a country has based on that is quite doable.

But how do you get the timezone for a specific city (preferably the timezone for any given lat/lng)? Other than looking up the pixel color in the map on the wikipedia article :)
Shared publiclyView activity