Kiribati moved across the International Date Line in 1995 so its whole territory could share a calendar day.
Kiribati is an island country spread across a large area of the Pacific Ocean. Before the change, its eastern islands were on a different calendar date from its western islands, making government, communication, and commerce difficult within one country. In 1995, the country shifted the date-line arrangement around its eastern islands.
The adjustment did not move the physical International Date Line worldwide. Instead, the line already zigzags around political territories, and Kiribati changed the time-zone boundaries used for its islands. The move made the Line Islands, including Kiritimati, one of the earliest inhabited areas to enter a new calendar year.
Kiribati is therefore often mentioned in discussions of who celebrates New Year's first. The exact order depends on time zones and daylight-saving rules, and “first country” can be less precise than naming the relevant island and time zone.