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Time is hard
February 7, 2012 10:22 AM   Subscribe

How long is a day around the world?

I don't know why I'm having such a hard time wrapping my head around the thinking here. What I want to determine is: if you could buy something anywhere in the world, as long as you bought it on February 10th, how long would the planet have, in total? Ie, how long does February 10th last, starting at the International Dateline and then going all the way around?

Using this as a baseline, New Years Day 2012, for example, starts at 5am on a Monday in Samoa. Then it happens everywhere else, obviously going all the way around the world and hitting American Samoa at 6am on a Tuesday. So is it 29 hours for that + 24 hours in a day? Is it that easy?

I could be missing something incredibly obvious here, or possibly I just lack basic math, but this is currently stumping me and my entire office. And google sucks for questions you don't know how to ask.
posted by Dormant Gorilla to Science & Nature (4 answers total) 9 users marked this as a favorite
 
Wikipedia's list of time zones by UTC offset says that times range from UTC-12:00 (Baker and Howland islands) to UTC+14:00 (the Line Islands and Tokelau).

So, for example, right now it's February 7. The earliest time it was February 7 anywhere in the world was, in UTC, 10:00 AM on February 6; fourteen hours ahead of that is midnight, February 6/7. The latest time that it will be February 7 is, in UTC, noon on February 8; twelve hours ahead of that is midnight, Feburary 7/8.

The difference is two days and two hours, or 50 hours. (You'd expect 48 in theory, but the date line isn't straight.) I'm assuming here that the UTC+14 places don't have daylight savings time (they're near the equator, so it seems unlikely). You could also make an argument that nobody lives in UTC-12 and the westernmost inhabited timezone is UTC-11, which would knock off an hour.
posted by madcaptenor at 10:31 AM on February 7, 2012 [3 favorites]


I think what you are trying to ask is "For how many hours is it February 7th somewhere in the world?"

World time zones are arranged in terms of their reference to "UTC" or coordinated universal time. The time zones go from UTC-12 to UTC+14. If you look at this map, you can figure out the following:

(1) It will first be 12:01am on February 7th in Kiribati, which is UTC+14.
(2) 14 hours later, it will be 12:01am in the London, which is UTC 0.
(3) 12 hours after that, it will be 12:01am at Baker Island, which is UTC-12.

That means that it will be 12:01, somewhere in the world, for a total of 26 hours. Now, add 24 hours to that total, because Baker Island will experience a full 24 more hours of February 7th. So the total is 50 hours.
posted by googly at 10:35 AM on February 7, 2012 [7 favorites]


The previous answers are correct, but I think I can explain it more clearly. The question is, as I understand it, "How long does it take to go from 12:00 AM at UTC+[max] to 11:59PM at UTC-[max]?"

Well UTC+[max] is UTC+14:00, and UTC-[max] is UTC-12:00. They're twenty-six hours apart.

UTC+14:00 will experience 12:00AM a full 26 hours before UTC-12:00.

It then takes 24 hours to get from 12:00AM to 11:59PM at UTC-12:00.

24 +26 = 50.

So the calendar will show any particular day at some point on the planet for fifty hours.

The reason it's 50 hours and not 48 hours is because, as observed, the International Date Line isn't straight, and there are places that have set their own time zones more than twelve hours ahead of UTC.
posted by valkyryn at 11:28 AM on February 7, 2012


You guys are the best. Thanks for explaining this so clearly; I just lost several bets.
posted by Dormant Gorilla at 1:12 PM on February 7, 2012


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