(See § Cartographic practice and convention below.) A person who goes around the world from east to west (the same direction as Magellan's voyage) would gain or set their clock back one hour for every 15° of longitude crossed, and would gain 24 hours for one circuit of the globe from east to west if they did not compensate by setting their clock forward one day when they crossed the IDL.Conversely, a west-to-east circumnavigation of the globe loses an hour for every 15° of longitude crossed but gains back a day when crossing the IDL.In much of this area, the IDL follows the 165°W meridian.Accordingly, Samoa, Tokelau, Wallis and Futuna, Fiji, Tonga, Tuvalu and New Zealand's Kermadec Islands and Chatham Islands are all west of the IDL and have the same date.For example, at UTC Thursday, it is Wednesday in American Samoa (UTC−), Thursday in most of the world, and Friday in Kiritimati (UTC ).
As a result, this atoll was renamed Millennium Island.Night and day is illustrative only; daylight hours depend on latitude and time of year.) The IDL is roughly based on the meridian of 180° longitude, roughly down the middle of the Pacific Ocean, and halfway around the world from the Greenwich meridian.In many places, the IDL follows the 180° meridian exactly.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.
These various deviations generally accommodate the political and/or economic affiliations of the affected areas. The IDL remains on the 180° meridian until passing the equator.The IUSSP also participates in conferences organized by the Asian Population Association (APA), the European Association for Population Studies (EAPS), the Latin-American Population Association (ALAP), the Population Association of America (PAA), the Union for African Population Studies (UAPS), and the International Statistical Institute (ISI).