Encyclopedic Entry

The date line helps divide the world into 24 time zones. Crossing the date line either adds 24 hours or subtracts 24 hours from a traveler's day.

Photograph by Jodi Cobb

Hawaii and Kiribati
The islands of the U.S. state of Hawaii lie almost directly north of the islands of the nation of Kiribati in the Pacific Ocean. They fall within the same lines of longitude.

However, because of a curve the date line makes around Kiribati, they are a day apart.

The date line, also called the International Date Line, is a boundary from which each calendar day starts. Areas to the west of the date line are one calendar day ahead of areas to the east.

The date line runs from the North Pole to the South Pole through the Pacific Ocean. It is not a straight line, however. The date line curves around several landmasses. For example, it curves around the islands that make up the nation of Kiribati, so that all regions of the country remain on the same day. The date line makes a big detour between Asia and North America in the Bering Strait. Cape Dezhnev, Russia, is always a day ahead of Cape Prince of Wales, Alaska, even though the landmasses are less than 80 kilometers (50 miles) apart.

The date line, which roughly follows the 180-degree meridian, is about halfway around the globe from the prime meridian, which measures 0-degrees longitude.


Term Part of Speech Definition Encyclopedic Entry

Bering Strait


narrow body of water connecting the Bering Sea and the Arctic Ocean, separating the continents of North America and Asia.



line separating geographical areas.

Encyclopedic Entry: boundary

date line


boundary running from the North Pole to the South Pole, roughly following the 180th meridian. The day begins west of the date line.

Encyclopedic Entry: date line



unplanned or temporary path.



direction in which the sun appears to rise, to the right of north.

International Date Line


line of longitude at roughly 180 degrees. East of this line is one day earlier than west.



distance east or west of the prime meridian, measured in degrees.

Encyclopedic Entry: longitude



line of longitude, dividing the Earth by north-south.

North Pole


fixed point that, along with the South Pole, forms the axis on which the Earth spins.

Encyclopedic Entry: North Pole

prime meridian


imaginary line around the Earth running north-south, 0 degrees longitude.

Encyclopedic Entry: prime meridian



any area on the Earth with one or more common characteristics. Regions are the basic units of geography.

Encyclopedic Entry: region

South Pole


fixed point that, along with the North Pole, forms the axis on which the Earth spins.

Encyclopedic Entry: South Pole



direction in which the sun appears to set.


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Kim Rutledge
Melissa McDaniel
Diane Boudreau
Tara Ramroop
Santani Teng
Erin Sprout
Hilary Costa
Hilary Hall
Jeff Hunt


Tim Gunther
Mary Crooks, National Geographic Society


Kara West
Jeannie Evers

Educator Reviewer

Nancy Wynne


Caryl-Sue, National Geographic Society


Dunn, Margery G. (Editor). (1989, 1993). "Exploring Your World: The Adventure of Geography." Washington, D.C.: National Geographic Society.

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