Lat/long to timezone mapper in Java and Swift and C#. Does not require web services or data files.
The "lat/long to timezone polygon mapping" is hardcoded, and we hope this rarely changes, but the changes to offsets and daylight savings changeover dates etc. (which are more frequent) are taken care of by your system libraries and so these are automatically kept up-to-date. From time to time, someone updates the files with the latest timezone polygons, but these rarely change...I think the most recent change is the Crimean peninsular.
99% of people using this project just need the one file:
(Swift) https://github.com/drtimcooper/LatLongToTimezone/blob/master/Classes/TimezoneMapper.swift
# Podfile
use_frameworks!
pod 'LatLongToTimezone', '~> 1.1'
In the Podfile directory, type:
$ pod install
Add this to Cartfile
github "drtimcooper/LatLongToTimezone" ~> 1.1
$ carthage update
For Swift 2.3 and earlier, use version 1.0.4 of the Podspec. For Swift 3 to 4.1, use version 1.1.3 of the Podspec. For Swift 4.2 or later, use the latest version.
In your code, you can do
import LatLongToTimezone
let location = CLLocationCoordinate2D(latitude: 34, longitude: -122)
let timeZone = TimezoneMapper.latLngToTimezone(location)