3 ms·

I think that if you want to use UTC, you should make it clear by adding "Z" (or "UTC") on the end of the numbers which tell you what time it is. This makes it m

I think that if you want to use UTC, you should make it clear by adding "Z" (or "UTC") on the end of the numbers which tell you what time it is. This makes it more clearly, avoiding some of the confusion they mention in that article. However, I think that local time should be used as well as UTC, for different purposes, but that the local time should just use solar time, rather than using time zones and DST.

layer8 1y ago
You can’t have standard seconds with solar time though (or minutes or hours), unless you live at the equator [0]. So it will be interesting to calculate at what local time your CI build is expected to complete, or if you have enough time to watch that 120-minute movie before whatever the equivalent of 10 o’clock would be in solar time. Or alternatively, each day would have to end at a different time, but then 12 o’clock wouldn’t be solar noon (or midnight). [0] http://wordpress.mrreid.org/2014/10/19/rate-of-change-of-day-length-with-latitude/ http://wordpress.mrreid.org/2014/10/19/rate-of-change-of-day...
- ianburrell 1y ago
  Solar time doesn't involve different lengths of seconds. The length of day and all the pieces doesn't change. Local solar time is effectively time zone on longitude. It is mean solar time. The downside of solar time is that 1 minute of time is 15 arc minutes which is roughly 17 mi east west. Which means need to deal with time zones in same metro area. The railroads invented time zones because dealing with local solar time was a pain. Minute accuracy is needed for time tables. We might be able to do it with computers, but it would require knowing the location of everything.
  - zzo38computer 1y ago
    When the minute accuracy is needed between different places, that is when UTC would be used. It is helpful for travel, and for many other purposes. For local stuff that does not involve precise measurement of timing, you can use solar time (and you can use a sundial), and you can do by the sun light (even, in summer it is more light and in winter it is dark early, you can use that, e.g. to go outside when it is light and don't need to turn on light inside, and in night time is dark you can sleep), and by the moon light (less commonly, but sometimes it is also meaningful and useful). Even for things that do use precise measurement of timing, UTC is not always appropriate; for some uses you will use TAI, or SI seconds instead of UTC seconds.
    - layer8 1y ago
      UTC seconds are the same as SI seconds. Or rather, there is no defined term "UTC second". You may be thinking of seconds-since-epoch counts that don’t include leap seconds, like in POSIX timestamps. That's not UTC though. UTC is a naming scheme for points in time, not a prescription for how to count seconds. What's true is that the exact number of seconds between future UTC times isn't known, because leap seconds aren't known arbitrarily in advance. But that doesn’t usually affect measurements of time. It does affect adding (large) SI-second counts to the current time to compute a future time. The exact UTC designation of that future time may not be known in advance.
  - layer8 1y ago
    Okay, that's mean solar time then, not actual (apparent) solar time.

layer8 1y ago

You can’t have standard seconds with solar time though (or minutes or hours), unless you live at the equator [0]. So it will be interesting to calculate at what local time your CI build is expected to complete, or if you have enough time to watch that 120-minute movie before whatever the equivalent of 10 o’clock would be in solar time. Or alternatively, each day would have to end at a different time, but then 12 o’clock wouldn’t be solar noon (or midnight). [0] http://wordpress.mrreid.org/2014/10/19/rate-of-change-of-day-length-with-latitude/ http://wordpress.mrreid.org/2014/10/19/rate-of-change-of-day...

ianburrell 1y ago
Solar time doesn't involve different lengths of seconds. The length of day and all the pieces doesn't change. Local solar time is effectively time zone on longitude. It is mean solar time. The downside of solar time is that 1 minute of time is 15 arc minutes which is roughly 17 mi east west. Which means need to deal with time zones in same metro area. The railroads invented time zones because dealing with local solar time was a pain. Minute accuracy is needed for time tables. We might be able to do it with computers, but it would require knowing the location of everything.
- zzo38computer 1y ago
  When the minute accuracy is needed between different places, that is when UTC would be used. It is helpful for travel, and for many other purposes. For local stuff that does not involve precise measurement of timing, you can use solar time (and you can use a sundial), and you can do by the sun light (even, in summer it is more light and in winter it is dark early, you can use that, e.g. to go outside when it is light and don't need to turn on light inside, and in night time is dark you can sleep), and by the moon light (less commonly, but sometimes it is also meaningful and useful). Even for things that do use precise measurement of timing, UTC is not always appropriate; for some uses you will use TAI, or SI seconds instead of UTC seconds.
  - layer8 1y ago
    UTC seconds are the same as SI seconds. Or rather, there is no defined term "UTC second". You may be thinking of seconds-since-epoch counts that don’t include leap seconds, like in POSIX timestamps. That's not UTC though. UTC is a naming scheme for points in time, not a prescription for how to count seconds. What's true is that the exact number of seconds between future UTC times isn't known, because leap seconds aren't known arbitrarily in advance. But that doesn’t usually affect measurements of time. It does affect adding (large) SI-second counts to the current time to compute a future time. The exact UTC designation of that future time may not be known in advance.
- layer8 1y ago
  Okay, that's mean solar time then, not actual (apparent) solar time.