How much is time wrong around the world?

A few years ago I went to Spain for the first time, and like many I was surprised by how late is dinner. The first night I dined almost alone in a restaurant at 8pm, going away just as people were starting to come in. Of course this can be mostly explained by cultural reasons, but the clearly later-than-usual summer sunsets must also have played a role in shaping the Spanish days.

Solar time vs. standard time

Solar time vs. standard time

At the time I’m writing, near the winter solstice, Madrid’s sunset is around 17:55, more than an hour later than the sunset in, for example, Naples, which is at a similar latitude. The same difference holds at the summer solstice and around the year. Just because it applies to most places I’ve been, a time like that in Naples feels more natural to me, and probably to most non-Spanish people. But is it?

Looking for other regions of the world having the same peculiarity of Spain, I edited a world map from Wikipedia to show the difference between solar and standard time. It turns out, there are many places where the sun rises and sets late in the day, like in Spain, but not a lot where it is very early (highlighted in red and green in the map, respectively). Most of Russia is heavily red, but mostly in zones with very scarce population; the exception is St. Petersburg, with a discrepancy of two hours, but the effect on time is mitigated by the high latitude. The most extreme example of Spain-like time is western China: the difference reaches three hours against solar time. For example, today the sun rises there at 10:15 and sets at 19:45, and solar noon is at 15:01.

So, why do some countries are forced to have such discrepancies? The only way to assign to a place a canonical time which follows our main assumptions is to observe the instant in the day when the Sun is higher in the sky, and call that 12:00. This is not practical for at least two important reasons.

Analemma of the sun

Analemma of the sun

One is that (solar) days do not all have the same length: the modern calendar compensates by letting midday oscillate a bit around the year: for example, midday in Naples goes from 11:47 in early November to 12:17 in early February. The difference between solar noon and clock noon is beautifully explained by an analemma, a picture with an exposure taken every few days at clock noon, showing how the sun moves in the sky not only in height (the north-south) direction due to the different seasons, but also in the east-west direction due precisely to the different lengths of the solar days.

More importantly, each city at a slightly different longitude would have a slightly different time. It seems strange that time systems with such a huge problem had ever been practical, but in the pre-industrial-revolution world, travels were so uncommon and slow that this problem was no more than a minor annoyance. But in today’s hyper connected (physically and virtually) world, it is obviously not an option.

The transition from apparent solar time, where all days have different lengths, to solar mean time, where midday wanders around 12:00, was caused by the proliferation of mechanical clocks in the early 19th century. The change to a time zone system, to solve the second problem, was caused instead by the telegraph and even more by the spreading of railway networks in the second half of that century; it’s not a coincidence that the first country moving to a common time was Great Britain.

Indeed, if we acknowledge that the two problems must be solved, the natural result is the current time zone system. The immediate consequence is that in the western part of the time zone the sun rises and sets later than in the eastern part. Normally, these differences amount to at most half an hour in either direction, but human geography sometime forces greater differences. In Spain’s case, to allow Spain to have the same time as central Europe, the difference can exceed ninety minutes. China instead decided in 1949 to adopt a single time zone, and to place its center in the richer east, forcing the less populated west to have an uncomfortable time. Indeed, though not officially recognized by the government, people in Xinjiang (China’s west-most region) follow a time zone closer to their apparent solar time, shifted by two hours from Beijing time.

Note: luckily, the map was uploaded on Wikipedia as SVG, so it was simply edited with a text editor to add the gradients (using Inkscape to match the objects with their ids). I do not usually like cylindrical projections (my favourite is Robinson‘s, and yes, I like coffee), but this time it made drawing gradients so much easier. And the Miller is a fair enough compromise.

77 thoughts on “How much is time wrong around the world?

  1. Steve Chisnall

    Needs to factor in daylight saving time and you forgot CWT (Central Western Time) in Australia (a few cities in central-west Oz that, like Nepal, use a quarter-hour offset instead of half-hour) Then there’s daylight saving time which in most places shifts the time a whole hour for summer-time but in one location (Australia’s Lord Howe Island) only shifts HALF an hour when switching from winter-time to summer-time.

  2. Stefano Post author

    The map doesn’t display anything related to DST (because, well, you’d need two maps for that). As for CWT (or CWST as Wikipedia calls it) in Oz (today I learnt Oz means Australia!), I’ll cite :

    The total population of that area is estimated at 200 people.

    So, that’s kind of below the threshold for this map. But thank you for noticing, it is interesting.

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  4. Keith Thomas

    It’s a work in progress, but I’ve created a website to propose my idea
    for a new system of time that gives the sun the respect it deserves.
    It is a serious effort, but I don’t expect to see it gain traction in
    my lifetime. The essence of the idea is a “smart clock” to give the
    daylight savings effect without biannual clock changes or time zones.
    It can easily be done now that mechanical clocks are no longer the
    latest technology. http://www.localdaylighttime.org/

  5. kalimero

    Well, I dont know. The natural human instict is wake up with the sun, and in Spain the sun rises at between 6:30-8:00 in the morning (and thats correct). In Poland during summer, for example, you can see the sun at 4:30 but, the sun set is at 18:00; so you wake up too early and you need to use electricity anyway. Sorry, but I dont agree with your opinion.

  6. Gary

    Very interesting map. I couldn’t help but notice how many of the more populated areas rest in locations that are a much closer match between the solar time vs. manmade time. I wonder if population settle in areas easier if the time matches closer to the natural rhythms?

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  10. Jonathan

    This is absolutely fascinating, how most people in the world live with their clock indicating an earlier time than what actually is. So that they feel like they’re waking up and going to bed later, but in fact they’re not.

    So I guess red areas are great for holidays, and green areas are great for working. I’m sort of lucky, I’m from Switzerland and we’re only 30 minutes early which is fine. But in summer we have this stupid DST, it’s nice to get extra sunlight during holidays evening, sure, but is absolutely terrible when you have to wake up to go to work before 7 AM and it’s still dark. Also we take supper at 6 PM here, long before our Spanish friends, even taking the difference in latitude in account ;)

    In any ways this is fascinating, and thank you very much for your work.

  11. Jorge

    There are social movements here in Spain that push to go back to GMT (which would be GMT+1 during DST), arguing that moving the clocks one hour backwards would results in a gain of productivity.
    I can agree with setting the time in mainland Spain as per its geographical meridian, but not based on the gain of productivity. A common working time is now 9-14, 15-18. The news in TV start at 21. If the clocks were moved one hour backwards, the working time would become 8-13, 14-17, and the TV news would be at 20, which means at the same solar time than now, so what’s the difference?

    On the other side, in modern times the interaction between different countries is much more important than one century ago, so there is a practical advantage for frequent travellers to have the same time as the nearby countries. For instance, a Spanish businessman dealing with colleagues in France, Germany, etc. is happy to have a common time, as it simplifies ordinary life.

    If the Spanish government decides to move the official time to GMT, it would make sense to make it in coordination with other neighbour countries, such as France, Belgium, Luxembourg, the Netherlands, and of course Andorra and Gibraltar, whose territories fall mainly west of meridian 7.5ºE. But I’m not sure that, in modern times, it would be an advantage to have, for instance, France in GMT and Germany in GMT+1, considering the continuous commercial exchanges between both countries.

    Last, it is important to say that we are assuming that timezones should be one hour width. This is an artificial convention. We could decide to divide the world in 8 time zones, each one separated 3 hours from the next one, instead of 24 main time zones separated 1 hour to each other. In that scenario, all Europe could fall in the same timezone, in the same way that all China share the same official time.

    Just one amendment to Manuela’s post (second one): noon in A Coruña on 20th June 2014 will be at 14:35, and not at 15:35 as you stated. For the rest, a very good post!

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  13. CARMEN

    I live in Spain.. and i think that in summer our shedule is fine because we have a lot of hours of sun and then we can go out at night.
    My family and friends eat at 15 00 and have dinner at 22 then we go out at night and wake up at 12 or so.
    (When you are on holydays)
    If not what we do is sleep a long siesta afterwork or going to the beach to rest and have dinner or go out at night

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  16. divisionbyzero0

    Chatham Islands NZ has a quarter offset, but about 30 minutes (90 minutes during DST) off of the solar time (it should be Gmt+12 rather than GMT+12:45)

  17. divisionbyzero0

    Btw how can the reddit version if the map is in the MapPorn?
    It’s a good knowledge map, but filtered here due to the “wrong” category in reddit

  18. Kenneth Udut

    Thank you for this map. I’ve been working on the concept and *hoping* someone dug in and did the math.

    It annoys me that a 5 year old can’t put a stick in the ground, look at the shadow, visually compare it with a standard reference building (like a school or house wall – most of which are nowadays build north/south east/west anyway – and know what time it is.

    Timekeeping should be THAT SIMPLE. And we have the technology to do so now.

    http://healthyclock.com/ I even threw this together a month ago or so as a rough draft of ideas.

    Your map illustrates the trouble we have at the moment. With all of the international committees available now, and the internet, there’s no reason that this can’t happen. Sure, there will be software changes but there are already, to correct for leap-seconds and such. It’d be a pain at first, but it would be worth it. Simplify time.

  19. Keith Thomas

    Here is my proposal, essentially the same as yours but further developed. Local time should be based on the sun but not on solar noon, rather on sunrise, keeping the benefits of Daylight Savings but without the ridiculous one hour jumps. And of course no time zone boundaries. “I rise with the sun” Thomas Jefferson. http://www.localdaylighttime.org/

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