imaginary line that demarcates the change of one calendar day to the next
Factsheet
Country Kiribati
no value
Russia
United States
no value
Russia
United States
Located in the administrative territorial entity Antarctic Treaty area
Coordinate location 0°N, 180°W
Country Kiribati
no value
Russia
United States
no value
Russia
United States
Located in the administrative territorial entity Antarctic Treaty area
Coordinate location 0°N, 180°W
Wikipedia
en.wikipedia.org › wiki › International_Date_Line
International Date Line - Wikipedia
5 days ago - The International Date Line (IDL) is the line extending between the South and North Poles that is the boundary between one calendar day and the next. It passes through the Pacific Ocean, roughly following the 180.0° line of longitude and deviating to pass around some territories and island groups.
NOAA National Ocean Service
oceanservice.noaa.gov › facts › international-date-line.html
What is the international date line?
The international date line, shown here as a yellow line, defines the boundary between calendar dates.
ELI5: Can somebody explain the international date line and why you lose/gain a day when you cross it?
It's arbitrary. I mean, there is a reason for it (more on that later), but there's no reason why it has to be that particular line. It could have been any of the infinite number of longitudinal lines. The reason why there would be one (not necessarily this one) is because there's a time zone for each hour (actually more, and actually they're not really arranged by lines, but this is ELI5), and so the only time when the whole entire globe would be on the same date is when it's between 12:00 midnight and 1:00 AM in the earliest zone. Because the latest zone is going to be, during that time, between 11:00 PM and 12:00 midnight. One more moment past 1:00 AM in the earliest zone, and now the latest zone is going to be past midnight into the next day. The reason why it's this particular line is because it's just defined that way. It's halfway around the world from London, which is where we've all basically agreed to define worldwide time from. So when it's noon in London, it's midnight of one day just to one side of the international date line, and midnight of another day just to the other side. More on reddit.com
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January 24, 2017What happens if you cross international date line multiple times from west to east in one day (because you have a very fast plane)
Crossing into a new time zone does not make any time suddenly pass. Local clocks may be set an hour different, but no time has passed just because you crossed over a line. If you cross over the international date line, and then 30 minutes later you cross over that same line again, then the only time that passed is 30 minutes. Time zones are measured as an offset relative to coordinated universal time (UTC). Sometimes also called "Zulu time". If you measure your time using UTC, the time will remain the same in all time zones. This is useful for operations that take place across multiple areas of the globe, so it tends to be used for military operations, international corporate operations, flight operations, and so on. More on reddit.com
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June 20, 2024ELI5: the International Date Line
The same way all the other time zone boundaries stay in the same place. That's what it is, the boundary between the furthest ahead time zone and furthest behind time zone. The difference between these time zones is 24 hours, so they're always the same time but a different date. More on reddit.com
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April 9, 2024If the International Date Line were a perfectly unbiased straight line, separating Siberia from Alaska, where would the Prime Meridian be located at?
Eyeballing it on Google Earth: the Diomedes islands are more or less in the middle of the Bering Strait. These are approximately 169W. The resulting prime meridian would be approximately 11E, passing through Verona, Italy. More on reddit.com
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December 31, 2023Why is there an international date line?
There is an International Date Line for two reasons. The first is that the Earth is a globe, so there must be some point where a day begins and ends. The second reason is because in a globalized world, everyone needs to know exactly what time it is in different places.
study.com
study.com › science courses › geology 101: physical geology
International Date Line | Definition & Location - Lesson | Study.com
Why is International Date Line not straight?
The International Date Line is not straight because if it were, it would divide several countries and force them to operate in two different days at once. The line used to do this to Kiribati, but the country eventually decided to push the date line east so that it could exist in just one time zone.
study.com
study.com › science courses › geology 101: physical geology
International Date Line | Definition & Location - Lesson | Study.com
Where is the International Date Line on a map?
The International Date Line goes down the middle of the Pacific Ocean on a world map. It starts at the North Pole, goes between Russia and Alaska, and then zigzags between several islands before heading to the South Pole.
study.com
study.com › science courses › geology 101: physical geology
International Date Line | Definition & Location - Lesson | Study.com
Videos
[GRADE 8] The International Date Line
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The International Date Line, Explained - YouTube
The International Date Line Explained | Johnny Harris
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International Date Line - YouTube
TimeAndDate
timeanddate.com › time zones › international date line
The International Date Line
The International Date Line (IDL) is an imaginary line on Earth’s surface defining the boundary between one day and the next.
Study.com
study.com › science courses › geology 101: physical geology
International Date Line | Definition & Location - Lesson | Study.com
January 30, 2017 - These time zones are the reason why when it is 9am in Los Angeles, it is noon in New York City. By necessity, one of these time zones will have to be the first to start a new day, and another will have to be the last. The point between those two time zones is where the International Date Line falls.
Esri Support
support.esri.com › en-us › gis-dictionary › international-date-line
International Date Line Definition | GIS Dictionary
An imaginary line, generally following the meridian of longitude lying 180 degrees east and west of the Greenwich meridian, where the date changes. The time zone east of the international date line is
Facebook
facebook.com › JohnnyHarrisVox › posts › the-international-date-line-explained › 1220351346123330
The International Date Line Explained
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Mapy
mapy.com › en
International Date Line (Notable parallel, meridian)
7. 5. 2026In the route planner and navigation for pedestrians and cyclists, you will now find warnings about difficult sections. So that you always know in advance whether there are passages along the way that could be beyond your abilities · Help • Legend • Mobile • Advertising • ...
US Naval Observatory
aa.usno.navy.mil › faq › international_date
The International Date Line
The International Date Line is the imaginary line on the Earth that separates two consecutive calendar days. That is, the date in the Eastern hemisphere, to the left of the line in the figure, is always one day ahead of the date in the Western hemisphere.
Utrecht University
webspace.science.uu.nl › ~gent0113 › idl › idl.htm
A History of the International Date Line
webspace.science.uu.nl · Nothing here except · webspace.science.uu.nl/~user/ · where user == solis_id · Thu Apr 2 11:38:40 CEST 2015 - webmaster@science.uu.nl - Faculty of Science, Utrecht University
Encyclopedia Britannica
britannica.com › philosophy & religion › humanities
International Date Line | Definition, Map, Importance, & Facts | Britannica
July 20, 1998 - International Date Line, imaginary line extending between the North Pole and the South Pole and arbitrarily demarcating each calendar day from the next. It corresponds along most of its length to the 180th meridian of longitude but deviates ...
AFAR
afar.com › places › international-date-line
Review of Crossing the International Date Line - AFAR
November 22, 2022 - It sits roughly on the 180-degree line of longitude in the middle of the Pacific Ocean, and its purpose is to separate calendar days based on the Greenwich Meridian half a planet away.
Lunar Tips
ftp.bills.com.au › home › news › what is the international date line?
What Is The International Date Line?
December 4, 2025 - The International Date Line (IDL), guys, is like this imaginary line on the surface of the Earth that mostly follows the 180-degree longitude. Picture this: you’re traveling around the world, and as you cross this line, the date changes!
Reddit
reddit.com › r/explainlikeimfive › eli5: can somebody explain the international date line and why you lose/gain a day when you cross it?
r/explainlikeimfive on Reddit: ELI5: Can somebody explain the international date line and why you lose/gain a day when you cross it?
January 24, 2017 -
This has been hurting my brain for the past few hours thinking about it, but I'm incredibly confused on the international date line. I full understand that you jump a day when crossing east to west and go back a day when you travel west to east, but why this specific line?
If it's the middle of the day, say, 6pm in Wellington, NZ, how does it make sense that the other side of the international date line it is 5pm in the previous day, when the distance between them isn't that far?
Edit: thanks for the replies! They have all been very helpful
Top answer 1 of 4
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It's arbitrary. I mean, there is a reason for it (more on that later), but there's no reason why it has to be that particular line. It could have been any of the infinite number of longitudinal lines. The reason why there would be one (not necessarily this one) is because there's a time zone for each hour (actually more, and actually they're not really arranged by lines, but this is ELI5), and so the only time when the whole entire globe would be on the same date is when it's between 12:00 midnight and 1:00 AM in the earliest zone. Because the latest zone is going to be, during that time, between 11:00 PM and 12:00 midnight. One more moment past 1:00 AM in the earliest zone, and now the latest zone is going to be past midnight into the next day. The reason why it's this particular line is because it's just defined that way. It's halfway around the world from London, which is where we've all basically agreed to define worldwide time from. So when it's noon in London, it's midnight of one day just to one side of the international date line, and midnight of another day just to the other side.
2 of 4
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It's just a definition. We define some longitude as being the start of the day and then each time zone west is one hour behind. We could set the date line to be somewhere else and everyone would just shift. It is somewhat similar to how 350 degrees is the same as -10 degrees on a circle. Instead of adding one hour to the reference time, subtract 23.
Suntrek
suntrek.org › earth-beyond › time-zones › international-date-line.shtml
International date line - Time zones - Earth & beyond - Sun|trek
Sun|trek (www.suntrek.org) is packed with spectacular images and movies of the Sun from solar space observations which can be downloaded for classroom work.'
David Darling
daviddarling.info › encyclopedia › I › International_Date_Line.html
International Date Line
The International Date Line is an imaginary line on the Earth's surface, with local deviations, along longitude 180 degrees from Greenwich.
Cute and Cuddly Wiki
cute-and-cuddly.fandom.com › wiki › International_Date_Line
International Date Line | Cute and Cuddly Wiki | Fandom
The International Date Line (IDL), also known as just the Date Line, is an imaginary line on the surface of the Earth opposite the Prime Meridian which offsets the date as one travels east or west across it.
Hawaii
pacioos.hawaii.edu › voyager › info › international_date_line.html
International Date Line
The International Date Line (IDL), also known simply as the Date Line, is an imaginary line on the surface of the Earth opposite the Prime Meridian (0°) that offsets the date as one travels east or west across it.
Utrecht University
webspace.science.uu.nl › ~gent0113 › idl › idl_imc_1884.htm
A History of the International Date Line - 1884 International Meridian Conference
In October 1884 astronomers and representatives from 25 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. When the meridian of the Royal Observatory ...
Medium
medium.com › passportpower › what-is-the-international-date-line-ca7978329c0f
🌍What is the International Date Line? 🌍
February 22, 2026 - ⛵ The International Date Line (IDL) is an imaginary boundary on Earth’s surface that runs from the North Pole to the South Pole, primarily through the Pacific Ocean. It serves as the demarcation …