The standard civil time zone that reaches New Year's Day first is UTC+14.
UTC+14:00 is the world's most advanced civil time offset from Coordinated Universal Time. The Line Islands of Kiribati, including Kiritimati, use this offset, so they enter January 1 before places in every other standard time zone. The date-line arrangement makes the easternmost Kiribati islands among the first inhabited places to celebrate a new year.
Kiribati moved the International Date Line eastward around its territory in 1994, allowing its widely separated islands to share the same calendar date. Kiritimati is therefore often described in media reports as one of the first inhabited places to welcome the new year.
UTC+14 is not the same thing as saying the islands are geographically farthest east. The International Date Line is an agreed civil boundary that bends around countries and island groups. Time-zone rules can also change, so a specific year's local observance should be checked against current official timekeeping information.