At the equinoxes, the first place to see daylight would be the uninhabited Millennium Island in Kiribati, which is the easternmost land located west of the IDL.Near the December solstice, the first places would be Antarctic research stations using New Zealand Time (UTC 13) during summer that experience midnight sun.These national zones do not extend into international waters.

For example, at UTC Thursday, it is Wednesday in American Samoa (UTC−11), Thursday in most of the world, and Friday in Kiritimati (UTC 14).

During the first hour (UTC –), all three calendar dates include inhabited places.

The IDL must therefore be observed in conjunction with the Earth's time zones: on crossing it in either direction, the calendar date is adjusted by one day.

For the two hours between and UTC each day, three different calendar dates are observed at the same time in different places on Earth.

Kiribati's easternmost islands, the southern Line Islands south of Hawaii, have the most advanced time on Earth, UTC 14 hours.

South of Kiribati, the IDL returns westwards but remains east of 180°, passing between Samoa and American Samoa.Proceeding from north to south, the first deviation of the IDL from 180° is to pass to the east of Wrangel Island and the Chukchi Peninsula, the easternmost part of Russian Siberia. Two US-owned uninhabited atolls, Howland Island and Baker Island, just north of the equator in the central Pacific Ocean (and ships at sea between 172.5°W and 180°), have the latest time on Earth (UTC−12 hours).(Wrangel Island lies directly on the meridian at 71°32′N 180°0′E, also noted as 71°32′N 180°0′W.) It then bends considerably west of 180°, passing west of St. The IDL circumscribes Kiribati by swinging far to the east, almost reaching the 150°W meridian.A 1995 realignment of the IDL made Caroline Island one of the first points of land on Earth to reach January 1, 2000 on the calendar (UTC 14).As a result, this atoll was renamed Millennium Island.In other places, however, the IDL deviates east or west away from that meridian. Aleutian Islands (Attu Island being the westernmost) and the Commander Islands, which belong to Russia. Thus, all of Russia is to the west of the IDL, and all of the United States is to the east except for the insular areas of Guam, the Northern Mariana Islands, and Wake Island.