If my computer takes its time from the internet, and the time zone is determined by the IP location, why doesn't using a VPN change the time zone, assuming the VPN server is in a different time zone?
21 Answer
Since this features apparently is specific to OS X, here’s a specific answer: Your location is not determined by IP addresses or whatever but via WiFi triangulation, just like modern smartphones do. An internet connection is required because the actual triangulation algorithm is an online service backed by a database of WiFi networks and their locations.
Some information on this is available in the official documentation. It’s stated there that this option relies on “Location Services”, which requires a WiFi adapter.