The Answer to ‘Where Is the International Date Line?’ Depends on How Much Time You Have

Traveling across the International Date Line (IDL) can get weird—seriously weird. Let’s say you’re looking for a change in scenery from the Edenic climes of Auckland and fall smitten with the whale-filled waters of Vancouver. As far as long-haul flights go, this one doesn’t seem too out of the ordinary—if you fly from New Zealand on a Tuesday, you’ll land in Canada the Monday before since you crossed the IDL from the left.

But that’s assuming you’ve crossed the line just once. Because of its jigsaw shape, your journey across the Pacific would more so resemble a game of time-travel hopscotch. All this to say, asking yourself where the International Date Line is, is only natural. And as it turns out, the origin story of this Parasaurolophus-headed imaginary line is more complicated than you’d think.

How the International Date Line came to be
Portuguese navigator Ferdinand Magellan’s surviving crew on the Victoria first documented the time-skipping phenomenon of global travel on Thursday July 9, 1522, whilst stopped at Cabo Verde. On track to become the first expedition to circumnavigate the world, the Magellan sailing came across a strange error in their log books on the home stretch of their nearly three-year journey: despite their fastidious record-keeping, they had somehow fallen back a day compared to the local calendar.

As it turns out, while they kept sailing

As it turns out, while they kept sailing westward, they continually encountered local noon later than they would have from their point of departure, as every 15 degrees of westward travel approximately corresponds with one hour of later local time. As they traveled a full 360 degrees around the world, their record-keeping ultimately fell a full 24-hours behind by the time they returned to Portugal.

Successive travels, observations, and a beloved Jules Verne novel all about the hijinks and perils of hot air balloon flight would later make common knowledge of the fact that circumnavigation results in the gain (if traveling westward) or the loss (if traveling eastward) of a day, and the idea that this difference in time would require its own place on our maps gradually came into fruition.

Mapping out time took further root in October 1884 during the International Meridian Conference held in Washington, DC, which convened 25 different nations to create a global standard for keeping track of time. The existing status quo was to measure time from a destination’s local meridian, its longitudinal position on Earth. At the precise moment the sun passes a destination’s meridian, which derives from the Latin word “meridies” meaning “midday,” that locale experiences its solar noon.

This subjective practice made for a logistical nightmare

But this subjective practice made for a logistical nightmare when it came to coordinating trade routes, communicating using the newfangled telegraph, and scheduling train times. To create this global standard, the conference sought to establish a “universal day,” a 24-hour date scale synchronized to the beginning and end of a day measured from a designated prime meridian, a zero-degree longitudinal line from which all time zones would be defined relative to.

As the late 19th century was the height of British sea power and the majority of countries present defaulted to using British maps for navigation anyway, Greenwich, England, was elected the location of the prime meridian, though not everyone left a fan—France did not adopt Greenwich Mean Time until 1911, and on the whole, the global adoption of a Coordinated Universal Time (UTC) would prove slow, taking several more decades to fully realize.

But the International Meridian Conference still provided a crucial basis for determining where the calendar turns on the globe, even if it did not formally set it. Theoretically, the same calendar day that Greenwich, England, experiences would end halfway across the globe where the 180th meridian lies, and thus the drawing of the prime meridian also implied the existence of its hypothetical twin, the International Date Line, though its actual plotting would prove to be neither straight nor straightforward.

More a boundary than a border Even prior

More a boundary than a border
Even prior to 1884 when an approximate meridian was established for the IDL, individual nations decided which day on the calendar they would observe primarily based on trade interests, and these preferences still impact the shape of the IDL to this day. For instance, when Spain claimed the Philippines as a colony, the new territory’s closest tie to its mother country lay in Acapulco, Mexico, which observes the prior calendar date to the rest of Asia.

As a result, the Philippines fell back a day to synchronize with the Western hemisphere, dragging a proverbial “date line” way out west. And after Mexico gained independence in 1821, the Philippines later switched back to observing the same date as its Asian neighbors in 1844 to align with new trade interests in China and the Dutch East Indies. Another prominent change to the global observance of dates came in 1867 when Alaska was purchased as a US territory.

Following the purchase, Alaska began abiding by the same calendar date as the United States rather than Russia, which at the time observed the Julian calendar, falling 12 days behind the US’s Gregorian calendar. The official date of the transfer took place on Saturday, October 7, 1867, on the Julian calendar, which was Saturday, October 19, 1867 on the Gregorian calendar to the west of the IDL.

Because Alaska moved to the east

But because Alaska moved to the east of the line, the date also shifted to Friday, October 18, 1867, a date now celebrated as the state holiday Alaska Day. That the Philippines sits on the same side of the date line as the rest of Asia and that Alaska observes the same date as the contiguous US are preferences the current iteration of the IDL still abides to. While the date line starts at the 180th meridian in the North Pole, it quickly curves to the east to slip between Russia and Alaska before course correcting west past the 180th meridian to make sure all the Aleutian islands fall west of the line.

While most map projections depict the part of the world the 180th meridian cuts through as open ocean, this region of Pacific is peppered with Oceanian island nations—each with their own preferences on the calendar date they’d like to observe. And these preferences continue to change to this day. Recent shifts to where the IDL is drawn include when it was pulled eastward to accommodate Kiribati, which wanted the entirety of the country under the same date.

On the eve of 1995, the eastern half of the country, which was a day behind its western half skipped Friday, December 31, 1994, and went straight into Sunday, January 1, 1995, to join its other half in being the first country to ring in the new year. The latest change to the IDL came in 2011 when Samoa and neighboring New Zealand territory Tokelau skipped to the west of the line by omitting Friday, December 30, 2011, altogether.

Because the IDL doesn’t function as a border

Because the IDL doesn’t function as a border that delineates the boundaries of a nation’s territory, its rell left up to “to each, their own” rules as the line is imaginary—and therefore flexible. Meaning, countries don’t have to ask permission or confer with any international law if they choose to change where they fall along in the line

So long as they pass a national law shifting time zones, reset their clocks accordingly, and publicize the change so mapmakers and other relevant parties can keep up, countries effectively dictate where the IDL is drawn through… just vibes.

Source: www.cntraveler.com