International Date Line

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The International Date Line (IDL) is the line extending between the South and North Poles that is the boundary between one calendar day and the next. It passes through the Pacific Ocean, roughly following the 180.0° line of longitude and deviating to pass around some territories and island groups. Crossing the date line eastbound decreases the date by one day, while crossing the date line westbound increases the date.

The line is a cartographic convention, and is not defined by international law. This has made it difficult for cartographers to agree on its precise course, and has allowed countries through whose waters it passes to move it at times for their convenience.^[1]