What is the International Date Line?
International Date Line (IDL) definition- It is an imaginary line that starts from the North Pole and ends at the South Pole and follows the 180 degree longitude. It passes through the Pacific Ocean. It is opposite to the Prime Meridian which is at 0 degree latitude.
A place just on the left side of the IDL will be a day ahead of the place just on the right side of the IDL. Tonga and Samoa are two islands in the South Pacific just 557 miles apart, and yet because they are on either side of the IDL, 11am in Tonga on Dec 8th equals 11am in Samoa on Dec 7th.
Around the world, lost 1 day
In 1519, Ferdinand Magellan and 241 men traveled around the Earth in their ship. They noticed that when they came back to their starting point, they had lost one day.
They had lost the day gradually, as they traveled around the Earth. They traveled with the rotation of the Earth, so their day was a little less than 24 hours, as they were traveling into the sunset.
So if you travel against the rotation of the Earth, your day is longer than 24 hours . For every 15 degrees you go west you add time while you lose time for every 15 degrees east.
The IDL came into being as a result of the International Meridian Conference in Washington DC in 1884.
Time zones- IDL goes zig zag to ensure that each country follows one time zone.
No law says that the IDL exists, but most maps show it.
Every place has the same date between 11:00 to 11:59 pm on the IDL.
It does not apply in space.
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