IDL (International Date Line) is a line imagined on surface of the Earth to set a boundary between day and night.
Drawn in 1884
The 180° meridian was selected as the International Date Line because it mostly runs through the sparsely populated Central Pacific Ocean. It was decided at the International Meridian Conference in 1884 in Washington, D.C. where 26 countries attended.
IDL is located in halfway around the globe from Prime Meridian (0° longitude) or you can say at about 180 degree east of Greenwich in London, UK as reference points of time zones. Another term used to represent this line is Demarcation Line.
IDL is not a Straight Line
IDL runs from North to South Pole and divide earth between Eastern and Western Hemisphere. To avoid any type of political or geographical borders related issues this line is drawn in zigzags. Another purpose of drawing this in zigzag shape is not to cut a country into half.
What will Happen if You Cross the Dateline?
When you cross date line from east to west, you add a day but if you cross from west to east, you subtract a day.
Depending on which time zone the country follows, the time difference on either side of the line is not always 24 hours. For example, if you travel the 1061 kilometers (659 miles) across the dateline from Baker Island to Tokelau you have to add 25 hours, or 1 day and 1 hour.
One Time and Three Dates
Different dates exist everyday on earth between 10:00 and 11:59 UTC. Therefore, at the same time three different calendars are used on Earth. For example as shown here;
- At 10:30 UTC on May 2, it is
- 23:30 (11.30 pm) on May 1 in American Samoa (UTC−11),
- 06:30 (6:30 am) on May 2 in New York (UTC-5), and
- 00:30 (0:30 am) on May 3 in Kiritimati (UTC+14).