What do you know about zero-degree longitude and the international date line?
The location of zero-degree latitude is obvious (the equator), but the location of zero-degree longitude is a purely political decision. It was variously placed at the Canary & Madeira Islands, the Azores, the Cape Verde Islands, Rome, Copenhagen, Jerusalem, St Petersburg, Pisa, Paris, and Philadelphia (among other places) before it finally settled down in London. No wonder I grew up as a young child thinking that Britain was the centre of the world.
It was in October 1884 that the Greenwich Meridian was selected by 41 delegates representing 25 nations at the International Meridian Conference held in Washington, D.C., United States to be the common zero of longitude and standard of time reckoning throughout the world.
But how did we decide on the international date line (IDL)which is the degree of longitude that determines the date of where you are at any given time?
By universally accepted convention, the IDL is essentially 180 degree longitude, but no international organisation, nor any treaty between nations, has fixed the IDL drawn by cartographers: the 1884 International Meridian Conference explicitly refused to propose or agree to any time zones, stating that they were outside its purview.
Conveniently the line 180 degree longitude runs through the least populated part of the globe – the middle of the Pacific Ocean. In many places, the IDL follows the 180 degree meridian exactly. In other places, however, the IDL deviates east or west away from that meridian. These various deviations generally accommodate the political and/or economic affiliations of the affected areas, usually small islands.
Conventionally, the IDL is not drawn into Antarctica on most maps.