algorithm for getting time zone from geo coordinates

Question

I want to write app where user can point any place on map (not only cities) and get timezone in that place.

What data structure (app will not have Internet connectiv

Answer 1

Well, if accuracy is not a requirement, why bother with a data structure ? Write a function which, given a longitude, returns the offset, expressed in hours, from the Greenwich meridian.

And if this doesn't work for you, I'd go with Joel Neely's answer.