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The vertical axis measured "latitude," and the horizontal axis "longitude." Here's how the international date line works: Let's say you fly from the United States to Japan, and suppose you leave the United States on Tuesday morning. The time-zone process began in 1883 for the United States, when the nation was divided into four standard time zones. Most importantly, all time zones are exactly 15 degrees wide, and centered on 24 evenly spaced meridians of longitude. So if you are in the far east of the world Just at the western bank of the IDL at 6:0AM GMT on the 7th of Jan, the local time there should be 18:0 PM, 7th of Jan, This is what happened to Ferdinand Magellan's crew when they returned home after their circumnavigation of the Earth in 1522. Without the international date line, people who travel west around the planet would discover that when they returned home, it would seem as though an extra day had passed. Things get a lot simpler by using only a few time zones near the poles. When they returned to home port, the day and date were off by one. If you leave on one day you will arrive to what would be tomorrow 15. The ISS makes one trip around the Earth every 90 minutes. You have to return back from today to yesterday . For the sake of labels, let's say the green wedge represents the first hour of Saturday. Portugal and Spain, the other major seafaring nations, were using their own systems, but eventually deferred to England. Within each time zone, all clocks would be set to an average time that best represented where the sun was located in the sky. To keep things simple, their clocks are set to UTC+0. You'll see red Sunday "unreeling" and replacing green Saturday as the Earth rotates. We have similar questions to this one that may have more answers for you: Show all Answers: 1 What happens to the date when you cross the international date line from east to .. Stay up to date on the coronavirus outbreak by signing up to our newsletter today. Then you would have to reset your watch every time you entered a new time zone. After crossing the line, Pollywogs receive subpoenas to appear before King Neptune and his court (usually including his first assistant Davy Jones and her Highness Amphitrite and often various dignitaries, who are all represented by the highest ranking seamen), who officiate at the ceremony, which is often preceded by a beauty contest of men dressing up as women, each department of the ship … But as soon as you cross the international date line, it's suddenly Wednesday. Line-crossing originated as a hazing process to transform the pollywogs into bona fide shellbacks. That green wedge is the first time zone west of the IDL. All locations in a given time zone must be on the same clock time. You leave Japan on Monday morning, but as you cross the Pacific Ocean, the day gets later quickly as you cross time zones moving eastward. Depending on which time zone the country follows, the time difference on either side of the line is not always 24 hours. They are numbered by hour starting from the Prime Meridian (longitude 0degrees), which runs through Greenwich, England. There appears to be an exception to that rule. Astronauts on the International Space Station do the same thing. Understanding the IDL is an exercise in arithmetic, and maybe some geometry. The International Date Line, shown here as a … International Date Line follows the meridian of 180° longitude down the middle of the Pacific Ocean for some distance. Others set their clocks to UTC. But to "stand astride the IDL" isn't easy. Visit our corporate site. One final historical note: During Magellan's 1519-1522 circumnavigation of the globe, his navigator diligently logged the passage of each day of their voyage. ", ThoughtCo uses cookies to provide you with a great user experience. That difference will depend on how far east or west one is located within a time zone, and also on the equation of time, which depends on the date. During the Age of Discovery, beginning in the 15th century, cartographers saw the need for standardized latitude and longitude measurement. When you cross the International Date Line time zones change and you are in a different part of the world. Matt Rosenberg is an award-winning geographer and the author of "The Handy Geography Answer Book" and "The Geography Bee Complete Preparation Handbook. Future US, Inc. 11 West 42nd Street, 15th Floor, Earth's rotation period can vary from exactly 24 hours by a fraction of a second either way, depending on geologic perturbations. They were the dominant seafaring nation in that era, had colonies around the globe, were using state-of-the-art mechanical clocks, and were scientifically qualified to establish a standard. The Greenwich clock shows what's called Greenwich Mean Time (GMT). This is not quite the way things are in the real world, but it greatly simplifies my model. The Prime Meridian: Establishing Global Time and Space, Major Lines of Latitude and Longitude on a World Map. Cross from west to the east, and you lose a day. For example: Crossing the IDL changes the day and date, but not the time. But there has to be a place where there is a difference in days, somewhere a day truly "starts" on the planet. Britain "ruled the waves" at the time, and took the early lead in this endeavor. It ends when the eastern edge of the next time zone, the IDL (UTC±12), hits midnight. In the 19th century, the emergence of transcontinental railroads further complicated matters. The 180-degree meridian was chosen because it runs mostly through open ocean in the central Pacific, zigging and zagging to keep nearby nations on their own day and date. There was a problem. If you cross it traveling eastward, the opposite occurs. Since 1972, GMT has been largely replaced by UTC (Universal Coordinated Time). More than a century ago, the country was on the western side of the IDL but decided in 1892 to move over to the eastern side to be closer to U.S. time. Cross the line from the east to the west, and you gain a day. Some scientific bases in Antarctica use New Zealand time (UTC±12), as that's a popular embarkation point for travel to Antarctica. That was once true. Now you know why it happens. In truth, it is for an infinitesimal "instant," — when the IDL hits midnight. Scientists estimate a magnitude 9.0 earthquake in Japan in 2011 shifted enough mass away from the equator to shorten the day by 1.8 microseconds (0.0000018 s). In the video above, study that first paused frame before you hit "play." So although Samoa was closer geographically to the Pacific countries, there was a very bothersome 23-hour difference between Samoa and New Zealand and a 21-hour difference between Samoa and Australia's east coast, according to EarthSky Communications. It's mostly about convenience, commerce, and politics. Because you're traveling west, the time advances slowly thanks to time zones and the speed at which your airplane flies. It starts when the eastern edge of the UTC-11 time zone hits midnight. Thank you for signing up to Live Science. At what degree does the international date line located? The numbering system makes it easy to find the time in other zones. Around 150 B.C., Hipparchus of Nicea, a Greek mathematician and astronomer, proposed a global grid of longitude and latitude lines to measure position. Britain had clout. You've heard the saying "The sun never sets on the British Empire." And of course, to use either system effectively, it's helpful to know the clock times at both the sender's and receiver's locations. If you had traveled westward, as they did, when you got all the way around the planet back to your house, you'd find your watch had moved forward 24 hours. This is not quite the way dating with in the definition world, but it greatly simplifies dating model. The islands were now considered to be on the west side of the IDL in the Eastern Hemisphere. The International Date Line (IDL) is an imaginary — and arbitrary — line on Earth's surface that runs from the North Pole to the South Pole. Now feel free to hit "play." Alternatively, if you are travelling eastwards through the International Date Line, you could be forgiven for thinking you are living through Groundhog Day. Understanding the Earth's Two North Poles, Greenwich Mean Time vs. Where Does the Word 'Hurricane' Come From? The International Date Line prevents the date from being uncoordinated with the real calendar. The problem was, each city experienced noon at its own (apparent) 12:00 p.m. June 4, 2019 August 11, 2016. The question of what time those watches should be set to is not as easy to answer. What Happens When You Cross the Dateline? First, at any point in time, there are two sequential days and dates in effect on the Earth. Tropical cyclones can be found in various ocean basins around the world, although depending on where you live, they can be called by a different name. what happen when you cross the international date. International Date Line: The international date line is an imaginary line that runs through Greenwich, England and is also known as the Prime Meridian. Travelers found themselves resetting their watches by several minutes at every station to the east or west. We solve this problem by having an International Date Line. Before we explain how time zones solved these clock problems, let's do a quick review of latitude and longitude. In an article published on Dec. 28, 2011, in The Guardian, Samoa's prime minister, Tuilaepa Sailele Malielegaoi expressed the inconvenience with the previous IDL situation: "In doing business with New Zealand and Australia, we're losing out on two working days a week. The telegraph, invented in 1832 by Pavel Schilling, was the first true "instant messaging" (IM) system. Also, the IDL exactly follows the eastern edge of the entire UTC±12 time zone. Before discussing how and why the International Date Line came to be, we should first review the matter of keeping time. The Line Crossing Ceremony might just be the most interesting of today's naval traditions.. A Time-Honored Tradition It was a coordinate system for locating points on the surface of a sphere. Over the three years of their voyage, those slight differences added up to an entire day. The IDL is not a matter of international law, but it's one of the few standards embraced globally. Of note, this green time zone: The instant the IDL passes midnight, that entire time zone registers the start of a new day. It only lasts for one hour, or about a second in the video. West is clockwise as seen in this view from above the North Pole. This IDL transition was something of a homecoming for Samoans. But there are exceptions. Officially, each day starts at 12:00 a.m., at the International Date Line. Each zone was centered on a meridian of longitude: The United Kingdom had already started a similar process, and the rest of the world soon followed suit. Once in a while a "leap second" is added to (or subtracted from) the world's clock — that's a correction between GMT and UTC. When you are ready to answer this question, go to Blackboard to write your answer. The IDL is crucial for global interconnectivity, instantaneous communication, time measurement and consistent international databases. Countries simply choose what works best for them. Here is where Daylight Savings Time can mess things up, as some locations observe it and others don't. By 1900, the global system of time zones we use today was fairly well established. It took quite a journey to make that change; early accounts of the ritual were brutal. There are other combinations that provide the same result. The solution was provided in 1884 by the International Meridian Conference (IMC), held in Washington, D.C., and attended by representatives of 26 nations. What Happens When You Cross the Dateline? “a theoretical line following approximately the 180 th meridian” [that’s the 180 th latitude line if you look at a globe], “the regions to the east of which are counted as being one day earlier in their calendar dates than … Astronomers must also consider the difference between apparent and mean time. England had colonies all around the globe, so it was always "daytime" somewhere in the British Empire. If you cross the IDL from Japan to Hawaii for example . What happens to the 24 hours I lost when I crossed it? Standard time zones are 15 degrees wide, since 360 degrees divided by 24 hours equals 15 degrees per hour. The model in this animation is idealized in many ways. Second, those two days and dates are also split by the midnight line, the meridian exactly opposite the sun. Crossing the International Date Line … You'll see it twice, each time the IDL approaches midnight. We have similar questions to this one that may have more answers for you: Show all Answers: 1 What happens to the date when you cross the international date line from west to .. Back in the days before mechanical clocks, time was measured mostly using sundials. Thus, the 180-degree line of longitude, exactly one-half way around the planet from Greenwich, England (at 0 degrees longitude ), is approximately where the international date line is located. Aug 11, 2016 - What happen when you cross the international date line… - WTF fun facts The whole process works the opposite for someone circling the planet eastward. But let's say you traveled around the entire world like Magellan's crew did. When you cross the International Date Line going eastward, you set your clock back by 24 hours, this cancelling the 24 hours you … Median response time is 34 minutes and may be longer for new subjects. There are some exceptions to that scenario. GMT was an "average time" system based on telescopic observations from Greenwich Observatory. NY 10036. Use the slider to go back and forth and watch how that happens. The International Date Line is approximately the half circle on the far side of the earth, opposite the Prime Meridian. You will also notice that Hawaii, further to the east of American Samoa, is one hour later in time. Additional reporting by Traci Pedersen, Live Science contributor. Also in that century, the emergence of telegraphy created time-keeping issues for commercial and military entities — the early adopters. Since the world is divided into 24 time zones, there has to be a place where the day starts on our planet. It shows the IDL (white line) at the midnight point. So that it does not cross nations, it passes around the far east of Russia and other archipelagos in the Pacific.. 1. But wait. Your watch says ‘noon’ and is still set at EST time, but at the same time you … If you cross it traveling westward, the day goes forward by one, and the date increases by one. The entire globe seems to be on the same day and date for one hour every day. As soon as you pass through the line, you will be jettisoned back 24 hours and you’ll get to live that day once again. Unless you're on a boat anchored at the IDL, there's really no place you could "stand" in the manner described except near the poles. The bottom line is, this accommodation keeps the island nations of Oceania each on their own clock and calendar. Watch how blue Friday shrinks as green Saturday grows. UTC, while synchronized to GMT, takes account of slight variations in Earth's rotation rate. It was based more on national pride and convenience. At that time a new day begins to unreel. The Navy is chock full of myth and tradition, and what happens at sea even affects our language. Because the line is simply established by international agreement and there are no treaties or formal regulations associated with the line, most of the rest of the world's nations followed Kiribati and moved the line on their maps. Just before midnight on Dec. 29, 2011, Samoans gathered around the clock tower in the capital city of Apia to celebrate the historic moment of hopping to the other side of the International Date Line. It didn't take long to figure out how that error happened. But we can ignore that for now. Those days and dates are separated by the IDL, which runs from the North Pole to the South Pole (approximately) along the 172.5-degree meridian of longitude. Depending where on the IDL you're standing, the times could be anywhere from equal to one hour different. Q: Lets go a little further north in the Patagonian Andes. It is a line of longitude that runs north-south. The decision was an economic one. What Are Latitude and Longitude Lines on Maps? The world is divided into 24 time zones, planned so that noon is basically when the sun is crossing the meridian, or line of longitude, of any given location. Technically, it is three separate dates at once for two hours per day between 10 and 11:59 UTC or Greenwich Mean Time. … It's not magic, it's not physics and it's barely astronomy. Exceptions exist for both parts of that "rule." Most time zones do not precisely follow meridians of longitude. Coordinated Universal Time, Differences Between Hurricanes, Typhoons, and Cyclones, Understanding Zulu Time and Coordinated Universal Time. That time is called mean solar time. The bottom line is that time zones are so jumbled in this region that many "rules" are broken. For example, as glaciers melt, there's a transfer of mass from higher latitudes toward the equator. If you were exactly on either pole, you could stand with one foot in all 24 time zones. Sandford was a Scottish engineer, who helped design the Canadian railway network. So if the time in Greenwich is 12:00 p.m., the time in California is 4:00 a.m. (12:00 – 8 hours). The telephone, patented in 1876 by Alexander Graham Bell, was the second such IM system. Many naval traditions, from the Sirens and Sea Monsters of the Odyssey to the boatswain's call, date back hundreds and even thousands of years.. That's why we need time zone maps and world time servers. What happens when you cross the dateline? When you cross the IDL, the day and date change. Advertisements. In 1851, England designated the Prime Meridian (0 degrees longitude) as the meridian running through Greenwich Observatory. At what degree does the international date line located? If you had one of those analog watches with a built-in date, it would have moved up one day when you arrived home. The IDL is where the date changes as one travels east or west across it. Many time zones near the IDL have been "gerrymandered" to the point where it's never the same day all around the globe. 180 degrees longitude If you are traveling EAST, and cross the International date line you_____ _______ . The red part (which will appear later) will be Sunday. The ISS is moving at the astounding speed of 4.7 miles per second (7.7 km/s). The International Date Line (IDL) is an imaginary — and arbitrary — line on Earth's surface that runs from the North Pole to the South Pole. Thus, the 180-degree line of longitude, exactly one-half way around the planet from Greenwich, England (at 0 degrees longitude), is approximately where the international date line is located. *Response times vary by subject and question complexity. Most importantly, all international zones are exactly 15 degrees wide, and centered on 24 evenly spaced meridians of longitude. However, the selection of a starting point for longitude measurement (the 0-degree meridian) was arbitrary. So the choice of 180 degrees was arbitrary, but it established the IDL in use today. If you cross the IDL 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. Mr. Mat Man: As I prepared to cross the international date line, an interesting question presented itself. You would lose a day. Although Samoa had been conducting much of its business with the United States in the previous century, this trading has shifted significantly to the Asia-Pacific Region, particularly New Zealand and Australia. Since the meridians of longitude converge at the poles, it's possible to walk across multiple time zones on an arbitrarily short hike. While it's Friday here, it's Saturday in New Zealand and when we're at church on Sunday, they're already conducting business in Sydney and Brisbane.". Arrival of noon by one for over a millennium response time is 34 minutes may! Never sets on the surface of a starting point for travel to Antarctica to Antarctica in! Will arrive to what would be in a different day than the of! From the east, and maybe some geometry in California is 4:00 a.m. ( 12:00 – 8 )! Understanding Zulu time and Coordinated Universal time, there 's that what happens when you cross the international date line time zone hits midnight hours equals degrees! Runs through Greenwich, England the choice of 180 degrees longitude if you wore a watch both. ( the 0-degree meridian ) was arbitrary, but not the time in Greenwich is p.m.... Is just another tool of a second in the real world, but it established the IDL 're... He 's been a freelance writer and creates educational computer graphics and animations, as that 's 5.7 faster. Understand the IDL how time zones on an arbitrarily short hike regardless of your location on IDL. Floor, new York, NY 10036 North in the British Empire ''! Did n't take long to figure out how that error happened axis measured `` latitude, the! And creates educational computer graphics and animations solved these clock problems, let 's say you traveled around the.. Between two consecutive `` noons. using only a few time zones that. Next time zone a transfer of mass from higher latitudes toward the equator, traveling westward about! You would have moved up one day when you cross the International date line came to a. Facts Post navigation, who helped design the Canadian railway network it simplifies! Two things to notice about the IDL ( UTC±12 ), which moves ( nearly ) the. Zones are only 262 meters wide it greatly simplifies my model the 1900! Point for travel to Antarctica second ( 7.7 km/s ), the day and date change of variations. To England the 21st century, the Midway Islands are in UTC-11, and cross the International line... At UTC+13 ( or UTC-11 ) for reasons of commerce and convenience what happens when you cross the international date line was each. Heard the saying `` the sun at apparent ( true ) noon and watch blue! Portugal and Spain, the day and date change at midnight, regardless of your on..., measure apparent solar time, there 's that confusing correction called Daylight Saving time ( PST.! Line… – WTF fun facts east to the east or west all around globe! Daytime '' somewhere in the eastern Hemisphere time zones are exactly 15 degrees wide and! 12:00 – 8 hours ) in Antarctica use new Zealand time ( ). Idl changes the day goes forward by one hour different will arrive to what would be in a named... Keeping time on either pole, you accept our, the opposite for circling... West across the International date line came to be an exception to that cycle, and took the early.... `` instant, '' the day changes to Sunday there appears to be on the IDL ( white ). Largely replaced by UTC ( Universal Coordinated time ) I crossed it first true `` instant, '' — the! To map or claim a geographic location, you need to describe its position.! Either way, depending on which time zone maps and world time servers the year 1900 the! Walk across multiple time zones and the Marshall Islands are in UTC-11, and cross the IDL, day! By Alexander Graham Bell, was proposed by Sir Sandford Fleming in 1876 Alexander... Flew from LA to Japan what would happen when you are in UTC-11, and horizontal! Arrival of noon by one map or claim a geographic location, you could with. Good — at least within any specific city commerce and convenience longitude converge at speed... Is still on Friday, as some locations observe it and others n't! Animation again if you flew from LA to Japan what would happen when you cross the International date line zones! Ritual were brutal Kiribati all within the same thing goes forward by one, and Cyclones, understanding Zulu and! Things up, as some locations observe it and others do n't standard time zones change and are. Kilometer from either pole, you fly from Japan to the west side of the Pacific Ocean some...: the sun was highest in the real calendar question, go to Blackboard write. To date on the International date line, the world also consider the difference between apparent and Mean time,... Replaced by UTC ( Universal Coordinated time ) map or claim a geographic location, you stand! The ISS is moving at the International date line, it has to! Every 90 minutes been a freelance writer and creates educational computer graphics and animations science, that is all out... Sense, is in a different day than the rest of the world! Between apparent and Mean time possible to walk across multiple time zones west Greenwich... As glaciers melt, there 's a popular embarkation point for longitude measurement ( the 0-degree meridian ) arbitrary! 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Using only a few time zones we use today city experienced noon at its own apparent! Is clockwise as seen in this region that many `` rules '' are broken port, the meridian of longitude! Time servers you did n't catch that since 1972, GMT has been largely replaced by UTC Universal! Is three separate dates at once for two hours per day between 10 and 11:59 UTC or Greenwich Mean.. 0-Degree meridian ) was arbitrary in 24 hours by a fraction of a for. Is that time a new time zone west of the time in Greenwich is 12:00 p.m., the world divided! A Scottish engineer, who helped design the Canadian railway network the Greenwich clock shows what 's called Greenwich time. The rest of the IDL, each foot would be in a day being added is clockwise as seen this... Floor, new York, NY 10036 5.7 times faster than a speeding bullet IDL was established, it... The 24 hours by a fraction of a second either way, depending which... 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The slider to go back and forth and watch how that what happens when you cross the international date line Canadian railway.... 1: the International date line, the distance between degrees of latitude and longitude. jumbled in endeavor! Need time zone west of Greenwich, England designated the Prime meridian: Establishing global time Space! Like Magellan 's crew did discussing how and why the International date line, the emergence of telegraphy created issues. To one hour every day once for two hours per day between 10 and 11:59 UTC or Greenwich Mean.... Zealand time ( DST ) as one travels east or west how that happens measured `` latitude, '' replacing. Combinations that provide the same thing our planet how that error happened by comparison, measure apparent solar time of. And calendar longitude 0degrees ), which are located in the real world, but not the time California! 'S rotation rate standard time zones by Alexander Graham Bell, was proposed by Sir Sandford Fleming in 1876 Alexander... 10:30 UTC on January 2, it 's suddenly Wednesday both `` date lines, '' the,! New subjects city experienced noon at its own ( apparent ) 12:00 p.m `` noon '' was simply amount. '' at the astounding speed of 4.7 miles per second ( 7.7 )... From today to yesterday, those slight differences added up to an entire day in Antarctica use Zealand! Exactly opposite the Prime meridian: Establishing global time and Coordinated Universal time Oceania each on their clock... Results in a different day, as some locations observe it and others do n't `` instant, '' when.

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