Kiribati is widely associated with the first inhabited midnight of the New Year because some of its islands use UTC+14.
The Line Islands, including Kiritimati, lie on the eastern side of the International Date Line but use a time zone 14 hours ahead of Coordinated Universal Time. As a result, their calendar date advances earlier than in most populated places.
Kiribati moved the International Date Line around its territory in 1994 so that its widely separated islands would share the same calendar day. The change helped improve administration and communication between the Gilbert, Phoenix, and Line island groups.
The exact phrase “first country” can be misleading because time-zone boundaries and inhabited locations matter. Kiribati is the standard answer in New Year coverage, especially when referring to Kiritimati, but other Pacific islands enter the new year soon afterward.