What Is The International Date Line?

The International Date Line (or the IDL) is the term that describes an imaginary line from the north to the south on the Earth's surface. It is exactly opposite the Prime Meridian and is approximately in line with the 180th meridian.

The International Date Line is also responsible for offsetting the date as a person travels east or west along it. In reality, it is not a straight line; it zigzags around populated regions like for instance around Russia and certain islands in the Pacific Ocean.

The west of the International Date Line is always a calendar day behind the east side. Accordingly if one travels east of the line a day is subtracted and if one crosses to the west a day is added. This is the cause of much confusion for those unfamiliar with this time zone boundary. The first ever date line problem was faced by Ferdinand Magellan. His ships logs were always meticulously compiled but the dates did not tally. This discrepancy generated so much excitement that even the Pontiff sent a delegation to explain this oddity to Magellan.

To explain the International Date Line, the concept of time zone should be known. As example if someone leaves New York by plane at a certain time and he reaches Los Angles just a little while later on the clock, he would be very much surprised. The reason is that the United States is divided into four time zones which were adopted in 1833. The zones were –eastern, central, mountain and pacific. The division was on meridians, the imaginary lines that run around the earth through the north and south poles. The time kept in each belt varies exactly an hour from the belt next to it.

The whole world is divided into time zones exactly as the United States is. Every 15 degrees as one goes around the world, in terms of meridians, there should be a new time zone.

It starts in Greenwich, England which has 0 degree meridian running through it. Exactly the opposite side of the world from Greenwich is an imaginary line called "International Date Line". If someone cross the line moving west, he would loss a whole day and if he moving east, he would gain a whole day.