UTC+14 is the time zone that reaches January 1 first among inhabited places.
UTC+14:00 is the world's most advanced civil time zone. It is used by Kiribati's Line Islands, including Kiritimati, also called Christmas Island. When the date changes there, locations west of the International Date Line are still on December 31.
Kiribati shifted the date-line arrangement of its islands in 1994 so that the country could share the same calendar date. The change placed the Line Islands on the side of the date line that observes UTC+14, making them famous for welcoming the new year early.
The phrase “first” depends on whether one means inhabited locations, land, or the official civil date. UTC+14 is the standard answer for the inhabited time-zone question; it is not a claim that every location on Earth changes date simultaneously.