3 ms·

Unless you're within a few feet of the longitude of the center of the timezone, this is already the case. That ship sailed, back in the railroad era when we de

Unless you're within a few feet of the longitude of the center of the timezone, this is already the case. That ship sailed, back in the railroad era when we decided to standardize time away from mean solar time. If we assume that the Gregorian calendar remains in use for as long as it's already been in use, the total accumulated error would likely be on the order of minutes. We could use a monotonic time scale like TAI for literally centuries and nobody would notice except astronomers, and arguably it would simplify astronomical corrections too because the underlying scale would be monotonic, which it isn't presently.

klodolph 6y ago
> That ship sailed, back in the railroad era when we decided to standardize time away from mean solar time. I’ll make the case here that we still use mean solar time, we just quantize it and push it around for political reasons. In any case, using time zones just means that your clock is off by maybe a half hour or 45 minutes in the lower US, and given the natural variation for sunrise and sunset, that doesn’t seem like an outrageous amount of error for temperate latitudes. Granted, there are a few places in the world with larger differences, like Spain or western China, or Argentina for some reason. Changes in the period of the Earth’s rotation have been estimated based on records of eclipses from as far back as the 8th century, which show that the Earth’s rotational speed is slowing down. Trying to extrapolate from fifty years of atomic time is going to give you the “on the order of minutes” estimate which is likely wrong. If you are trying to work out the error over five centuries, you should probably be using the best available data, which is records of eclipses and ephemerides.
- kevin_thibedeau 6y ago
  It's more than 45 minutes on the western extremes in the EST, CST, and MST zones.
  - klodolph 6y ago
    I chose the wording “maybe a half hour or 45 minutes” to make it crystal-clear that the exact number was not relevant to the argument, in a vain effort to avoid responses like this one. Perhaps I should be more explicitly vague in the future. HN is tiring.
    - danaliv 6y ago
      No, you’re absolutely right. As someone who uses UTC professionally in aerospace ops, trust me when I say your clock is still definitely tied to solar time even if it’s “off” by whatever. Try using UTC exclusively—I don’t just mean on your servers, I mean in every single aspect of your life—and you’ll see what I mean.
  - deleted 6y ago
    [deleted]
throwaway894345 6y ago
Yeah, I'm musing abotu the possibility of using monotonic time. Right now, our time system conveys implicit information about the "solar time of day" (whether or not its daylight in the locale) as well as season (January is winter in the Northern Hemisphere). For monotonic time, you would have to use some sort of conversion function to recoup that information. As we both noted, certain monotonic time systems could be used which deviate very little from solar time such that the accumulated error would only make a difference (for the purpose of recouping that aforementioned implicit information) at very large time scales, which is a problem we already face with inflation (1950s dollars are not the same value as 2021 dollars and we all seem to manage alright with that).

klodolph 6y ago

> That ship sailed, back in the railroad era when we decided to standardize time away from mean solar time. I’ll make the case here that we still use mean solar time, we just quantize it and push it around for political reasons. In any case, using time zones just means that your clock is off by maybe a half hour or 45 minutes in the lower US, and given the natural variation for sunrise and sunset, that doesn’t seem like an outrageous amount of error for temperate latitudes. Granted, there are a few places in the world with larger differences, like Spain or western China, or Argentina for some reason. Changes in the period of the Earth’s rotation have been estimated based on records of eclipses from as far back as the 8th century, which show that the Earth’s rotational speed is slowing down. Trying to extrapolate from fifty years of atomic time is going to give you the “on the order of minutes” estimate which is likely wrong. If you are trying to work out the error over five centuries, you should probably be using the best available data, which is records of eclipses and ephemerides.

kevin_thibedeau 6y ago
It's more than 45 minutes on the western extremes in the EST, CST, and MST zones.
- klodolph 6y ago
  I chose the wording “maybe a half hour or 45 minutes” to make it crystal-clear that the exact number was not relevant to the argument, in a vain effort to avoid responses like this one. Perhaps I should be more explicitly vague in the future. HN is tiring.
  - danaliv 6y ago
    No, you’re absolutely right. As someone who uses UTC professionally in aerospace ops, trust me when I say your clock is still definitely tied to solar time even if it’s “off” by whatever. Try using UTC exclusively—I don’t just mean on your servers, I mean in every single aspect of your life—and you’ll see what I mean.
- deleted 6y ago
  [deleted]

throwaway894345 6y ago

Yeah, I'm musing abotu the possibility of using monotonic time. Right now, our time system conveys implicit information about the "solar time of day" (whether or not its daylight in the locale) as well as season (January is winter in the Northern Hemisphere). For monotonic time, you would have to use some sort of conversion function to recoup that information. As we both noted, certain monotonic time systems could be used which deviate very little from solar time such that the accumulated error would only make a difference (for the purpose of recouping that aforementioned implicit information) at very large time scales, which is a problem we already face with inflation (1950s dollars are not the same value as 2021 dollars and we all seem to manage alright with that).