The rarest time zone on Earth (both by land mass using it and by population using it) is UTC-12:00, the time zone that ends every day on the calendar (aka the last to ring in every new year). It has several inhabited islands within its standard boundaries, but each of those islands chooses to use a different time zone. This leaves two uninhabited islands, Howland and Baker Islands in the South Pacific, as the only land masses to use the zone.
https://magazine.tagheuer.com/en/202...ne-on-earth-2/