Kiribati is commonly described as among the first places to welcome the New Year because part of the country uses UTC+14.
The relevant area is the Line Islands, including Kiritimati, also known as Christmas Island. Their civil time is Line Islands Time, which is UTC+14, the furthest-ahead standard time zone in common use. As a result, midnight arrives there before it reaches most of the world.
Kiribati moved the International Date Line eastward around its territory in 1995 so that its widely separated islands would share the same calendar date. Before that change, the country’s island groups could be on different sides of the date line, complicating administration and communication.
The phrase “first country” can oversimplify the geography because Kiribati spans several island groups and time zones. The precise claim is that its Line Islands are among the earliest inhabited places to enter a new calendar year, not that every part of Kiribati reaches midnight simultaneously.