180th meridian

Antimeridian

The International Date Line zigzags around the 180th Meridian.

The 180th meridian or antimeridian^[1] is the meridian 180° east or west of the Prime Meridian, with which it forms a great circle dividing the earth into the Western and Eastern Hemispheres. It is common to both east longitude and west longitude. It is used as the basis for the International Date Line because it for the most part passes through the open waters of the Pacific Ocean. However, the meridian passes through Russia and Fiji as well as Antarctica.

Starting at the North Pole and heading south to the South Pole, the 180th meridian passes through:

Co-ordinates (approximate)	Country, territory or sea	Notes
90°0′N 180°0′E / 90.000°N 180.000°E / 90.000; 180.000 (Arctic Ocean)	Arctic Ocean
71°32′N 180°0′E / 71.533°N 180.000°E / 71.533; 180.000 (Russia)	Russia	Chukotka Autonomous Okrug — Wrangel Island
70°58′N 180°0′E / 70.967°N 180.000°E / 70.967; 180.000 (Chukchi Sea)	Chukchi Sea
68°59′N 180°0′E / 68.983°N 180.000°E / 68.983; 180.000 (Russia)	Russia	Chukotka Autonomous Okrug
65°02′N 180°0′E / 65.033°N 180.000°E / 65.033; 180.000 (Bering Sea)	Bering Sea
52°0′N 180°0′E / 52.000°N 180.000°E / 52.000; 180.000 (Amchitka Pass)	Amchitka Pass	Passing just east of Semisopochnoi Island, Alaska, United States (at 51°57′N 179°47′E / 51.950°N 179.783°E / 51.950; 179.783 (Semisopochnoi Island))
51°0′N 180°0′E / 51.000°N 180.000°E / 51.000; 180.000 (Pacific Ocean)	Pacific Ocean	Passing just east of Nukulaelae atoll, Tuvalu (at 9°25′S 179°52′E / 9.417°S 179.867°E / -9.417; 179.867 (Nukulaelae atoll)) Passing just west of the island of Cikobia, Fiji (at 15°43′S 179°59′W / 15.717°S 179.983°W / -15.717; -179.983 (Cikobia))
16°9′S 180°0′E / 16.150°S 180.000°E / -16.150; 180.000 (Fiji)	Fiji	Islands of Vanua Levu, Rabi, and Taveuni
16°59′S 180°0′E / 16.983°S 180.000°E / -16.983; 180.000 (Pacific Ocean)	Pacific Ocean	Passing just east of the island of Moala, Fiji (at 18°33′S 179°57′E / 18.550°S 179.950°E / -18.550; 179.950 (Moala)) Passing just west of the island of Totoya, Fiji (at 19°0′S 179°52′W / 19.000°S 179.867°W / -19.000; -179.867 (Totoya)) Passing just east of the island of Matuku, Fiji (at 19°10′S 179°47′E / 19.167°S 179.783°E / -19.167; 179.783 (Matuku))
60°0′S 180°0′E / 60.000°S 180.000°E / -60.000; 180.000 (Southern Ocean)	Southern Ocean
78°13′S 180°0′E / 78.217°S 180.000°E / -78.217; 180.000 (Antarctica)	Antarctica	Ross Dependency, claimed by New Zealand

180° Meridian, Taveuni, Fiji

The meridian also passes between (but not particularly close to):

the Gilbert Islands and the Phoenix Islands of Kiribati;
between North Island and the Kermadec Islands of New Zealand;
between the Bounty Islands and the Chatham Islands, also of New Zealand.

The only place where roads cross this meridian, and where there are buildings very close to it, is in Fiji.

Software representation problems

Many geographic software libraries or data formats project the world to a rectangle; very often this rectangle is split exactly at the 180th meridian. This often makes it non-trivial to do simple tasks (like representing an area, or a line) over the 180th meridian. Some examples:

The GeoJSON specification strongly suggests splitting geometries so that neither of their parts cross the antimeridian.^[2]
In OpenStreetMap, areas (like the boundary of Russia) are split at the 180th meridian.

Notes

↑ The word antimeridian can also mean the meridian opposite to any given meridian. E.g. 20° west is the antimeridian of 160° east.
↑ "RFC 7946 - The GeoJSON Format".

Circles of latitude / Meridians

Equator

Equator

Equator

W 0° E

90°

180°

90°

180°

0°

5° N

45°

5° S

45°

Time measurement and standards
Chronometry Orders of magnitude Metrology
International standards	Coordinated Universal Time offset UT ΔT DUT1 International Earth Rotation and Reference Systems Service ISO 31-1 ISO 8601 International Atomic Time 6-hour clock 12-hour clock 24-hour clock Barycentric Coordinate Time Barycentric Dynamical Time Civil time Daylight saving time Geocentric Coordinate Time International Date Line Leap second Solar time Terrestrial Time Time zone 180th meridian
Obsolete standards	Ephemeris time Greenwich Mean Time Prime meridian
Time in physics	Absolute time and space Spacetime Chronon Continuous signal Coordinate time Cosmological decade Discrete time and continuous time Planck time Proper time Theory of relativity Time dilation Gravitational time dilation Time domain Time translation symmetry T-symmetry
Horology	Clock Astrarium Atomic clock Complication History of timekeeping devices Hourglass Marine chronometer Marine sandglass Radio clock Watch Water clock Sundial Dialing scales Equation of time History of sundials Sundial markup schema
Calendar	Astronomical Dominical letter Epact Equinox Gregorian Hebrew Hindu Intercalation Islamic Julian Leap year Lunar Lunisolar Solar Solstice Tropical year Weekday determination Weekday names
Archaeology and geology	Chronological dating Geologic time scale International Commission on Stratigraphy
Astronomical chronology	Galactic year Nuclear timescale Precession Sidereal time
Units of time	Century Day Decade Fortnight Hour Jiffy Lustrum Millennium Minute Moment Month Paksha Saeculum Second Shake Week Year
Related topics	Chronology Duration music Mental chronometry Metric time System time Time value of money Timekeeper

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180th meridian

Software representation problems

See also

Notes