international date line
An imaginary line, generally following the meridian of longitude lying 180 degrees east and west of the Greenwich meridian, where the date changes.
International Date Line
Traveling across the International Date Line from west to east, time jumps ahead one whole day and traveling across from east to west, time goes back one whole day.
International Date Line
The International Date Line (IDL) is an imaginary north-south line (at the 180th meridian), in the Pacific Ocean, at which the date changes. The east side of the IDL is a calendar day earlier than the west side.
International Date Line A line drawn almost parallel to the 180 degree longitude meridian that marks the location where each day officially begins. The location of the International Date Line was decided upon by international agreement.
In addition to the Prime Meridian, which is the 0° mark in today's longitudinal system, the International Date Line is also an important marker.
The first zone begins at the International Date Line (180°, using the geographic coordinate system). The zones are numbered from west to east, so zone 2 begins at 174°W and extends to 168°W.
North of the equator and west of the International Date Line are the numerous small islands of Micronesia, including the Caroline Islands, the Marshall Islands and the Mariana Islands.
That opposite meridian is the base of the international date line, which separates world halves in two different days. Again, this line is somewhat irregular in order to keep national territories (mostly Pacific islands) in a single timezone.
The first zone starts at the International Date Line (180 degrees east) and the last zone, 60, starts at 174 degrees east. Northings are determined separately for the areas north and south of the equator.
To the east time progressively became later in a day and to the west time progressively became earlier in a day. This resulted in the creation of an interesting phenomenon at the 180° line of longitude - the International Date Line.
At the opposite side of the globe from the prime meridian (at 180 degrees) is the International Date Line. Latitude and longitude can be expressed in degrees, minutes and seconds or in decimal fractions. See the first figure at the right.
 See also: International date line, Longitude, Meridian, Equator, Latitude
  
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