Kiribati is known for New Year's Eve celebrations in the UTC+14 time zone.
Kiribati's Line Islands, including Kiritimati, use Line Islands Time, which is UTC+14. This places them among the first inhabited places to reach a new calendar date. The position is a result of the International Date Line's political and geographic arrangement, not because the islands physically move faster around the Earth.
In 1995, Kiribati shifted the date-line arrangement for its eastern islands so that the country could share the same calendar day across its territory. The change helped coordinate national administration and reduced the previous situation in which parts of Kiribati were separated by a calendar day.
Kiritimati is often called Christmas Island, but it is not Australia's Christmas Island. It is part of Kiribati and lies in the central Pacific. “First to celebrate” can be imprecise because celebrations occur across many islands and time zones; UTC+14 is the specific fact behind the claim.