When you cross the IDL, the day and date change. If you cross it traveling westward, the day goes forward by one, and the date increases by one. If you cross it traveling eastward, the opposite occurs.
The IDL happened for much the same reasons as the emergence of the Internet — it works, and it makes life a little bit easier. Before discussing how and why the International Date Line came to be, we should first review the matter of keeping time. Back in the days before mechanical clocks, time was measured mostly using sundials. People relied on the definition that "noon" was when the sun was highest in the sky,
Single date line due south.
One "day" was simply the amount of time between two consecutive "noons. The problem was, each city experienced noon at its own
Single date line Depending on longitude, adjacent cities could have a time of, say, Near the equator, traveling westward by about 1, miles 1, kilometers delays the arrival of noon by one hour. Ajax listener not called dating
Also in that century, the emergence of telegraphy created time-keeping issues for commercial and military entities — the early adopters. The telegraph, invented in by Pavel Schilling, was the first true "instant messaging" IM system.
Single date line over great distances using electricity, which moves nearly Single date line the speed of light. 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.
Before we explain how time zones solved these clock problems, let's do a quick review of latitude and longitude. It was a coordinate system for locating points on the surface of a sphere. The vertical axis measured "latitude," and the horizontal axis "longitude.
During the Age of Discovery, beginning in the 15th century, cartographers saw the need for standardized latitude and longitude measurement.
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If your intent is to map or claim a geographic location, you need to describe its position unambiguously. Britain "ruled the waves" at the time, and took the early lead in this endeavor. Portugal and Spain, the other major seafaring nations, were using their own systems, but eventually deferred to England.
Latitude was less an issue than longitude, since there was no dispute about where the poles "Single date line" 90 degrees north and 90 degrees south and equator latitude 0 degrees were located. However, the selection of a starting point for longitude measurement
Single date line 0-degree meridian was arbitrary. It was based more on national pride and convenience.
InEngland designated the Prime Meridian 0 degrees longitude as the meridian running through Greenwich Observatory. 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.
Single date line heard the saying "The sun never sets on the British Empire.
England had colonies all around the globe, so it was always "daytime" somewhere in the British Empire. By the latter part of the 19th century, scientists, railroads and other emerging industries felt the need for a global standard of time. The first such system, using 24 standard time zones, was proposed by Sir Sandford Fleming in Sandford was a Scottish engineer, who helped design the Canadian railway network.
His system wasn't officially sanctioned by any global entity, but by it spawned the adoption of the time zone system in use today. Nation by nation, the world bought into Fleming's idea. Within each time zone, all clocks would be set to an average time that best represented where the sun was located in the sky. That time is called mean solar time. Sundials, by comparison, measure apparent solar timesometimes called true solar time. The time-zone process began in for the United States, when the nation was divided into four standard time zones.
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. Bythe "Single date line" system of time zones we use today was fairly well established. Increasing global connectivity demanded some universal system of time measurement, and standard time zones were the answer. Most time zones do
Single date line precisely follow meridians of longitude.
They zig and zag as needed to keep islands, smaller countries and large metropolitan areas on the same clock time — an obvious concession to convenience. Standard time zones are 15 degrees wide, since degrees divided by 24 hours equals 15 degrees per hour. They are numbered by hour starting from the Prime Meridian longitude 0degreeswhich runs through Greenwich, England.
The numbering system makes it easy to find the time in other zones. When atomic clocks were invented in the s, it became possible to measure time with an accuracy better than that provided by the rotating Earth. GMT was an "average time" system based on telescopic observations from Greenwich Observatory. 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. Earth's rotation period can vary from exactly 24 hours by a fraction of a second either way, depending on geologic perturbations.
For example, as glaciers
Single date line, there's a transfer of mass from higher latitudes toward the equator. As with a figure skater who slows his spin rate by extending an arm or leg, the law of conservation of angular momentum requires a reduction of the spin rate to compensate for this redistribution of mass.
Scientists estimate a magnitude 9. Astronomers must also consider the difference "Single date line" apparent and mean time. That difference will depend on how far east or west one is located within a time zone, and also on the equation of timewhich depends on the date. But again, to understand the IDL, we can ignore these complications.
We all know the day
Single date line date change at midnight, regardless of your location on the planet. But to use a global time zone system with an IDL, the day and date have to be separated at two locations — you can't split a circle into two parts with a single "cut. The IMC selected the degree meridian as the other "cut," not because it was directly opposite the Prime Meridian any meridian Single date line have been that other "cut".
The 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.
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So the choice of degrees was arbitrary, but it established the IDL in use today. The bottom line is, this accommodation keeps the island nations of Oceania each on their own clock and calendar.
But there are exceptions. Just before midnight on Dec. As the clock struck The
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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. So although Samoa was closer geographically to the Pacific countries, there was a very bothersome hour
Single date line between Samoa and New Zealand and a hour difference between Samoa and Australia's east coast, according to EarthSky Communications.
So in an effort to better synchronize their work weeks with their main trading partners, the two island countries countries decided to hop "Single date line" the IDL. In an article published on Dec.
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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. This IDL transition was something of a homecoming for Samoans. More than a century ago, the country was on the western side of the IDL but decided in to move over to the eastern side to be closer to U. So for years, Samoans witnessed the last sunset of the day and were the last to ring in the New Year — now they are one of the first.
Unfortunately, there will always be some inconvenience living so close to the IDL: Now there is a hour difference between Samoa — located on the western part of the Samoa island chain — and American Samoa on the eastern side. Fractional time zones are used in 16 locations around the globe. Countries simply choose what works best for them. In the video above, study that first paused frame before you hit "play.
For the sake of labels, let's say the green wedge represents the first hour of Saturday. The blue part of the Earth is still on Friday. The red part which will appear later will
Single date line Sunday. That green wedge is the first time zone west of the
Single date line. West is clockwise as seen in this view from above the North Pole.
Of note, this green time zone:. The instant the IDL passes midnight, that entire time
Single date line registers the start of a new day. All locations in a given time zone must be on the same clock time.
There are some exceptions: But we can ignore that for now. The model in this animation is idealized in many ways. Most importantly, all time zones are exactly 15 degrees wide, and centered on 24 evenly spaced meridians of longitude. The International Date Line (IDL) is an imaginary — and arbitrary If you cross it traveling westward, the day goes forward by one, and the date. '#1 Trusted Dating Site. Every day, an average of singles marry a match they found on eharmony.
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