International Date Line

American  

[in-ter-nash-uh-nl deyt lahyn] / ˌɪn tərˈnæʃ ə nl ˈdeɪt ˈlaɪn /

noun

1. a theoretical line following, with occasional deviations, the antimeridian, the regions to the east of which are counted as being one day earlier in their calendar dates than the regions to the west.

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International Date Line British  

noun

1. Also called: date line.  the line approximately following the 180° meridian from Greenwich on the east side of which the date is one day earlier than on the west

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International Date Line Scientific  

/ ĭn′tər-năsh′ə-nəl /

1. An imaginary line on the Earth's surface that is internationally agreed upon as the place where each new calendar day begins. The line extends from the North to the South Pole through the Pacific Ocean, roughly along the 180th meridian. The calendar day to the east of the line is one day earlier than it is to the west of the line. The International Date Line was established at the International Meridian Conference in 1884 in order to standardize time, especially for the purpose of travel.

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Etymology

Origin of International Date Line

First recorded in 1875–80

Example Sentences

We started in the Pacific at the International Date Line in the Kingdom of Tonga.

From The Wall Street Journal • Nov. 27, 2025

But he does acknowledge that they were guided by a theory that Noonan had failed to account for how the International Date Line would affect his calculations.

From National Geographic • Jan. 30, 2024

The island is south of Japan, west of the International Date Line and marks the boundary of the Pacific Ocean and the Philippine Sea.

From Seattle Times • May 24, 2023

The solution to this dilemma is the International Date Line, set by international agreement to run approximately along the 180° meridian of longitude.

From Textbooks • Oct. 13, 2016

The 100-plus players and coach Sonny Dykes missed the rest of Sunday when they crossed the International Date Line in the middle of the Pacific Ocean.

From Washington Times • Aug. 21, 2016