In OTL, longitudinal time zones (each ideally 15° wide, ±7½° around each of 24 main meridians) were introduced in the late 19th century when time tables for trains, for instance, began to require more precision and standardization across wider areas than a sundial could provide. The day had been divided into 24 equal hours long before that. This approximates solar noon at 12:00 except when daylight saving time is in effect or where timezones are shifted for political reasons.

In an ATL, how would it affect time-keeping and society as a whole if they also had 24 latitudinal time zones (each 7½° high, between two parallels) and their offsets would change regularly – e.g. 4 to 12 times a year in the US and most of Europe – to approximate sunrise at 00:00?

Assume that sunrise had always been considered the start of the day in the globally dominant culture, so it was absolutely reasonable to start the daily clock counter there.

While the equator and poles are natural extrema, the Greenwich meridian was arbitrarily selected. For the sake of familiarity and simplicity, let’s assume the 0° line in this ATL is equivalent to ours. Let the area bordered by i×7½° parallels, to the north and south, and by j×m±7½° longitudes, to the west and east, be known as a time segment.


London and Paris (hence England and France) would reside in the same time segment, but Scotland should be in the one to the north, Spain to the south of it.

In London, the earliest sunset is at 04:43 in June (03:43 without DST) and the latest at 08:06 in January and December currently. In New York City it’s between 05:24 (04:24 w/o DST) and 07:20 local time, i.e. 09:24 to 12:20 UTC. In Los Angeles it’s 05:41(–1) to 06:59, i.e. 12:41 to 14:59 UTC. (In Quito, Ecuador, the sun always rises between 05:54 and 06:17 and sets almost exactly 12 hours later every day, by the way. In Reykjavik, Iceland, it varies from 02:56 to 11:23 UTC.)

London would probably use the offsets –2, –1, ±0, +1 and +2 (i.e. 8 switches) throughout the year, where ±0 is about 6 hours ahead of OTL UTC. For NYC, it’s +3 or +4 through +6 (4 or 6 switches); LA +7 through +9 (4 switches). (In Quito the offset is always +5, whereas 16 Reykjavik needed 16 switches to cycle from –3 through +5 and back.)

I also asked a somewhat similar question where hours are not a constant length.

PS: Some countries tried multi-step DSTs in the mid 20th century, see British Double Summer Time and Central European Midsummer Time at Wikipedia.

  • 1
    $\begingroup$ I wonder if Jewish solutions to the problem would be helpful as the time of sunset is the beginning of the day. I don't understand the purpose of multistep daylight savings time. (This could be a function of the fact I don't understand the benefit of DST in any world) $\endgroup$
    – King-Ink
    Jan 25, 2016 at 17:09
  • $\begingroup$ I want less DST, not more. How do I get that?? I don't care if it's permanent DST where you spring forward but then never fall back again, or just abolish it all together. $\endgroup$
    – AndyD273
    Jan 25, 2016 at 18:11
  • $\begingroup$ @AndyD273 Me too, but that’s not the point. If the traditional cultural paradigm was that the day always starts with sunrise at 00:00, the occasional 23- or 25-hour day would not seem that strange as with our paradigm of midday at 12:00 and midnight at 00:00 (except for more than 6 “summer” months each year in many countries). $\endgroup$
    – Crissov
    Jan 25, 2016 at 19:08
  • $\begingroup$ Its an intriguing idea (I've never considered a latitude based timezone system before!), but it seems like a bit of a stretch. If the sun is so important, why would you pick a time system which causes the sun to rise at the meridian at 0:00, but results in the sun rising at some arbitrary time everywhere else in the world? Am I misreading the idea? $\endgroup$
    – Cort Ammon
    Jan 25, 2016 at 23:57
  • $\begingroup$ Arguably there is a point at each latitude where the sun rises at 0:00 UTC, it just shifts over the course of the year. $\endgroup$
    – Cort Ammon
    Jan 25, 2016 at 23:58

2 Answers 2

  • Commerce gets more difficult/grows more slowly when there are more distinct time zones. It is less conventient to arrange continent-wide transportation and communication networks.
  • People are irritated when they have to switch more often and remember how to re-set all their watches.
  • In the real world, many people wake up, have a relatively short breakfast, go to work or to school on a fixed schedule, and then get the late afternoon and evening off until it is time to sleep. Your scheme would give the breakfast and the work time more sunlight, at the expense of the leisure time. For a greater part of the year than now, all of the leisure time would be after sundown. That would be bad enough today, with electric lights in every home or street. Would it lead to widespread depression?
  • $\begingroup$ It totally depends on where you live and when are the usual business hours. If you got a “zero to eight” job in this ATL and live in NYC or Rome (both 41±0.7° N), you get over 9 to 15 hours of sunlight per day, so at least 1 hour after work (alas, probably wasted in commute). In London or Berlin (52±0.5° N and north of that), some winter days have (slightly) less than 8 hours from dawn till dusk, though. $\endgroup$
    – Crissov
    Jan 25, 2016 at 19:23
  • $\begingroup$ This or we all ignore the DST bit and set our watches to the sunrise. Effectively the same system but with different granularity. Figuring out what time it is in New York when you live in Cairo would be a bit of hassle involving haversines but in the time of cell phones we could just call to ask. $\endgroup$
    – King-Ink
    Jan 25, 2016 at 22:16

The ancient and accepted method of setting clocks is to set them to noon when the sun is directly overhead this lead to the longitudinal time zones. You are very clever to point out that if we set our clocks to the rising sun we would have different time zones based on latitude and longitude. They would also be based on altitude and obstructions to the horizon. Does the day start when the sun crosses the theoretical horizon or when it is visible?

Using an OTL (Orignal timeline?) example Orthodox Jews have been counting the being of a day bay the exact method but with nightfall. The Talmudic solution to the bizarrely complicated subject of when night begins is to call it when the stars are visible to end the Shabbat then three stars are visible just to be safe. The stunning thing here is that there are literally as many Shabbats as Orthodox. (if one counts eyesight as a factor) They use the goyish system for most other things. The equation of time

That seems like a big aside but it the exact issue the ancients of your world were tackling when they developed their system. Correct me if I am wrong but is the Daylight Savings system the society's attempt to have equal hours of the day?

That was my thinking here is my answer.

1) poor adherence

Farmers, The religious, and people without appointments would ignore Daylight savings and time zones and use the underlying system. Civilized meaning city people would get watches / phones that calculate it automatically. ATL Earthicans in countries marked gray in this map would also ignore it or maybe just the DLS part https://en.wikipedia.org/wiki/Daylight_saving_time_by_country https://en.wikipedia.org/wiki/Daylight_saving_time_by_country

1b) This just in, Your system actually makes more sense near the equator and so probably originated there so the map may be reversed.

2) More Travel confusion

North-south trips would be as annoying time wise as east-west ones. Would I get jetlag going to Florida?

3) New years eve would be a frightful mess

4) possible increases in north-south hostility and sense of otherness.

4a) advantages to equatorial peoples. Their times reflect "true" or solar time more closely.

4b People at high elevations, in mountainous terrains or in the north would have a system that less close reflect their experience.

That is what I got. Other than that I also agree with @o.m s take on it Depression and an awkward day. I think a lot of people would ignore it unless work or a doctor's appointment made them. .


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