Kiribati is among the first inhabited countries to celebrate New Year's Eve because parts of it use UTC+14, the world's furthest-forward standard time zone.
The relevant islands are in the Line Islands, including Kiritimati, also known as Christmas Island. Their position on the eastern side of the International Date Line means that their calendar date advances before it does in most other inhabited places. As a result, Kiritimati is frequently mentioned in global reports about the first New Year.
Kiribati is an island country spread across a huge area of the central Pacific. Its three island groups—the Gilbert, Phoenix, and Line Islands—were placed under a unified time arrangement in 1995, when the date line was adjusted around the country so that all of Kiribati would share the same calendar day.
The phrase “first country” can be misleading because time-zone comparisons depend on which island and standard-time rules are being considered. The UTC+14 Line Islands are the key reason Kiribati appears at the front of New Year lists.