180th meridian

The meridian at 180° longitude, opposite the prime meridian. It lies mostly in the Pacific Ocean and is followed approximately by the International Date Line.

International Date Line: A boundary where crossing generally changes the calendar date by one day. It follows the 180th meridian across much, but not all, of the Pacific.
Geographic coordinate system: A system locating positions on Earth with coordinates such as latitude and longitude. It defines how the 180th meridian is identified as a position line.
Bering Strait: A narrow sea passage separating Alaska from Russia and connecting the Pacific and Arctic oceans. The Date Line bends through this region rather than following the meridian strictly.
Date line: A boundary separating calendar dates across the Earth’s surface. Unlike the fixed 180° meridian, the International Date Line bends around territories.
Prime meridian: The 0° longitude meridian used as the reference for measuring longitude. The 180th meridian lies directly opposite this longitude reference.
UTC offset: The difference between a local time and Coordinated Universal Time, expressed in hours and minutes. Date boundaries near the meridian correspond broadly to large changes in local time.
Aleutian Islands: A volcanic island chain extending west from Alaska toward the Kamchatka Peninsula. The Date Line detours around the islands to keep Alaska and the Aleutians on the same date.
Equator: The great circle at 0° latitude, equally distant from the poles. It is a latitude reference circle, whereas the 180th meridian is a longitude line.
Longitude: A geographic coordinate measuring angular position east or west of a reference meridian. The 180th meridian is one line of constant longitude.
Time zone: A region that uses a shared standard time, usually defined by offset from UTC. Time-zone choices near the meridian interact with the date boundary.

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