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.
These include portions of the Republic of Kiribati, including Millennium Island in the Line Islands, as well as Samoa during the southern summer.
The first major cities to experience a new day are Auckland and Wellington, New Zealand (UTC 12; UTC 13 with daylight saving time).
American Samoa, the Cook Islands, Niue, and French Polynesia are east of the IDL and one day behind. It follows that meridian until reaching Antarctica, which has multiple time zones.
Conventionally, the IDL is not drawn into Antarctica on most maps.
The 15° gore that is offset from UTC by 12 hours is bisected by the nautical date line into two 7.5° gores that differ from UTC by ±12 hours.
Ships are supposed to adopt the standard time of a country if they are within its territorial waters within 12 nautical miles (14 mi; 22 km) of land, then revert to international time zones (15° wide pole-to-pole gores) as soon as they leave.
(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.
During the second hour (UTC –) one of the calendar dates is limited to an uninhabited maritime time zone twelve hours behind UTC (UTC-12).
According to the clock, the first areas to experience a new day and a New Year are islands that use UTC 14.