The date line is the logical consequence of the so-called Circumnavigator’s Paradox, which was known to scientists before it was witnessed for the first time by Antonio Pigafetta in the early 16th century.
One of only 18 crew members out of 237 to survive Ferdinand Magellan’s first circumnavigation of the globe, Pigafetta kept a diary throughout the voyage. When the ship Victoria made landfall at the Cape Verde islands after almost three years’ absence from lands accustomed to Western timekeeping, he noted: (Jacobs, NY Times)
“On Wednesday, 9th July (1522,) we … sent the boat ashore to obtain provisions … And we charged our men (that) they should ask what day it was.”
“They were answered that … it was Thursday, at which they were much amazed, for to us it was Wednesday, and we knew not how we had fallen into error. For every day I, being always in health, had written down each day without any intermission.”
Pigafetta then concluded, “As we were told since, there had been no mistake, for we had always made our voyage westward and had returned to the same place of departure as the sun, wherefore the long voyage had brought the gain of twenty-four hours, as is clearly seen.” (Magellan’s Voyage, Pigafetta)
“(T)he Europeans in the Sandwich Islands reckon time from West to East, brought through Canton, so that we who brought time from East to West, were a day behind them in reckoning, just as was the case in Kamtschatka and the Russian settlements.”
“The same difference was the case between neighboring cities of San Francisco and Port Bodega. When one must take into account the old and the new calendar, the reckoning of time from East to West here, Greenwich time, ship time, mean time, and apparent time, sun time and star time, the astronomical day, etc., it is not easy to say what is the time of day.” (Adelbert Von Chamisso; 1816; HHS)
In October 1884 astronomers and representatives from various countries convened in Washington at the International Meridian Conference to recommend a common prime meridian for geographical and nautical charts that would be acceptable to all parties concerned.
Twenty-six nations, represented by 41 delegates, participated in the conference; Luther Aholo (Privy Counsellor) and William DeWitt Alexander (Surveyor General) went to Washington as a commissioner from the Kingdom of Hawaii to the International Meridian Conference in 1884 (Alexander also represented the Republic of Hawaii in 1893-1894.)
The Greenwich Meridian was chosen for international use at the International Meridian Conference on October 22, 1884; “from this meridian longitude shall be counted in two directions up to 180 degrees, east longitude being plus and west longitude being minus.” (Resolution III, International Conference, 1884)
Given the North and South poles, which are approximately the ends of the axis about which the Earth rotates, and the Equator, an imaginary line halfway between the two poles, the parallels of latitude are formed by circles surrounding the Earth and in planes parallel with that of the equator.
If the circles are drawn equally spaced along the surface of the sphere, with 90 spaces from the equator to 90 degrees North and South at the respective poles, each is called a degree of latitude.
Meridians of longitude are formed with a series of imaginary lines, all intersecting at both the North and South poles, and crossing each parallel of latitude at right angles but striking the equator at various points.
While the Conference decided on the Prime Meridian through Greenwich, they did not determine its anti-meridian. 180 degrees east (and west) of Greenwich was the natural choice for the International Date Line.
However, neither the International Meridian Conference, nor any other subsequent global committee, ever sanctioned its ‘official’ use. (Jacobs, NY Times) No international agreement, treaty or law governs the precise location of the date line. (Ariel)
The International Date Line exists for a specific reason. It marks the time zone border where the date is actually changed by a whole day.
The International Date Line prevents the date from being uncoordinated with the real calendar. If you cross the date line during travel while you’re moving in an easterly direction, you must subtract a day, but if you cross the date line moving in the opposite direction – west – then you must add a day. Ultimately, it helps keep everyone across the world synced up with the real time. (WorldTimeServer)
Due to the lack of any international guide lines for the location of the date line, 20th-century map makers have tended to follow the recommendations of the hydrographic departments of the British and the American Navy.
Both departments regularly issue charts and pilot books for the Pacific Ocean region that represent the date line as a series of connected straight lines (or better ‘circle segments’). The earliest recommendations issued by these departments referring to the date line appear to date from 1899 and 1900.
Two adjustments of the date line took place in 1910 near the island chain of Hawai‘i and between Samoa and the Chatham Islands. (Utrecht University)
No record can be found as to when Hawai‘i decided it was east rather than west of the International Date Line, but presumably this occurred not too many years after Chamisso’s visit.
Moreover, according to Howse, “The date line as originally drawn had a kink to the westward of the Hawaiian Islands to include Morrell and Byers islands which appeared on nineteenth-century charts at the western end of the Hawaiian chain. It was then proved that they did not exist, so the date line was straightened out.” (Schmitt & Cox)
North of the Bering Strait, at the latitude of Wrangel Island (Ostrov Vrangelya, and considered part of Russia) that separates the East-Siberian Sea from the Chukchi Sea, the date line experienced some local adjustments during the early 1920s.
A Canadian expedition to colonize the barren island failed miserably and by 1926 the Russians had re-established their claim by settling the island with Russian-Siberian colonists.
The temporary adjustment of the date line in 1921 to bisect Wrangel Island would appear to indicate the initial recognition of the Canadian claim on this island by the British Hydrographic Department. (Utrecht University)
In 2011, Samoa changed the date line near them – as “the clock struck midnight (10:00 GMT Friday) as 29 December ended, Samoa and Tokelau fast-forwarded to 31 December, missing out on 30 December entirely.”
“Samoa announced the decision in May in a bid to improve ties with major trade partners Australia and New Zealand.
Neighbouring Tokelau decided to follow suit in October.” (BBC)
The change comes 119 years after Samoa moved in the opposite direction. Then, it transferred to the same side of the international date line as the United States, in an effort to aid trade.
The date line doesn’t just demarcate days; generally north of the equator severe tropical cyclones east of the date line are referred to as hurricanes, west of the date line they are caller typhoons (if a named hurricane crosses the dateline, it keeps the same name, but is then referred to as a typhoon.) (NOAA)