Calamares is a distribution-independent (Linux) system installer. Outside of the "big five" distro's, many smaller "boutique" distro's need an installer, and Calamares is a highly configurable one that they can use. There's a few dozen distro's that I know of that use it (although I've only actually installed maybe six of them).

One optional feature -- optional at the discretion of the distro which is deploying Calamares, that is -- is the use of GeoIP location to find the time zone of the device being installed. This is used to automatically set the clock, for instance. If it's not switched on, or there's no network, Calamares defaults to a location defined by the distro -- generally New York, although there's an Austria-based distro that I think defaults to UTC.

For years, the default and suggested GeoIP provider has been freegeoip.net. That service is shutting down -- well, being upgraded to a nicer API, at a different location, and with different access limitations. Older ISO images that have Calamares configured to use GeoIP with that service will cease to get usable GeoIP data on july 1st, 2018.

I don't actually know which distro's have GeoIP enabled, nor what provider they use.

However, the fact that this provider is shutting down prompted me to go over the existing code and make it more flexible and more general (prodding from Gabriel and Phil and Harald helped here as well). So Calamares is now ready to use more, and different, providers of GeoIP data. The providers can't agree on using "time_zone" or "timezone" or "TimeZone" as the attribute (JSON) or element (XML) name where the data lives, so there's a little bit more code and configuration needed. But you (as a distro) can now shop around and pick a GeoIP provider that respects your privacy.