4 ms·

Large parts of the world shift civil time by an hour twice a year. Drifting 1 day every 200,000 years doesn't sound like kicking the can down the road. If huma

Large parts of the world shift civil time by an hour twice a year. Drifting 1 day every 200,000 years doesn't sound like kicking the can down the road. If human civilisation still exists by the time we've reached just 1 hour of difference we'll be occupying multiple bodies throughout the solar system, if not further afield, and have to have come up with a new time system anyway. Even the length of a second varies because of relativity.

kijin 5y ago
Yeah, we already do the Feb 29 thing every 4 years. We make exceptions to that rule every 100 years, and an exception to the exception every 400 years. Those leap years make larger oscillations than any leap second ever tries to correct for, and we're totally fine with that. Adding another exception every 200,000 years doesn't sound unexpected at all.
- deleted 5y ago
  [deleted]
- user-the-name 5y ago
  They do not. Those adjust the calendar, not the clock.
  - kijin 5y ago
    A calendar is just a clock that measures longer durations of time.
    - user-the-name 5y ago
      Irrelevant in this context.
    - FabHK 5y ago
      But one of these adjustments aims to keep mid day at noon, while the other aims to keep solstice around 21 Dec. You could skip leap years and still have the sun up at noon, while your solstice date drifts away. Or, you could skip leak seconds and still have the solstice on 21 Dec, but have your noon drift away from mid day.
      - iso1631 5y ago
        very few locations have the sun directly above at 12 (based on a timezone offset from UTC), and just as many places have it directly above at 12 based on an offset from TAI The sun is overhead from Greenwich at 12:06 GMT today, it varies by about half an hour from 1143 to 1214 through the year (ignoring daylight saving) I'm not sure if varying from 1150 to 1221 would be any better. Even after a minute of leap seconds (say 100 years) the point where the "sun is overhead at 12:00:00" point for points at UK/Ireland latitude would have moved about 10 miles from its current position. in a few millenia the timezone would be wrong, but easilly corrected by either skipping a "spring forward" or "fall back" time.
- throw0101a 5y ago
  > Yeah, we already do the Feb 29 thing every 4 years. Except it's not every four years. It's every four years, but it is skipped if the year is divisible by 100… but not skipped if it is also divisible by 400—which ended up biting people in 2000 which was a leap year: * https://slate.com/technology/2016/02/the-math-behind-leap-years.html https://slate.com/technology/2016/02/the-math-behind-leap-ye...
  - JadeNB 5y ago
    > > Yeah, we already do the Feb 29 thing every 4 years. > Except it's not every four years. > It's every four years, but it is skipped if the year is divisible by 100… but not skipped if it is also divisible by 400—which ended up biting people in 2000 which was a leap year …. Unless they edited, that's exactly what your parent said, after you cut off the quote: > Yeah, we already do the Feb 29 thing every 4 years. We make exceptions to that rule every 100 years, and an exception to the exception every 400 years.
throw0101a 5y ago
> Large parts of the world shift civil time by an hour twice a year. Yes, and how many things break every time this common thing occurs? Or every four years when February 29 rears its ugly head. And these are code paths that should be well tested because of their frequency.
- iso1631 5y ago
  POint is we can cope with the sun directly overhead at 14:20 (as it is today in Madrid), or at 11:20 (as it is in Warsaw in November) A drift of a minute over a lifetime makes no difference. We should just use TAI (with timezone offsets) for general time and be done with it. Even today UT1 is widely different to UTC (183ms), so it's not like using UTC is accurate. Why is 183ms an acceptable difference (no leap milliseconds), a couple of hours (timezone sizes), one hour (DST), but we have to correct for 40 seconds each century?

kijin 5y ago

Yeah, we already do the Feb 29 thing every 4 years. We make exceptions to that rule every 100 years, and an exception to the exception every 400 years. Those leap years make larger oscillations than any leap second ever tries to correct for, and we're totally fine with that. Adding another exception every 200,000 years doesn't sound unexpected at all.

deleted 5y ago
[deleted]
user-the-name 5y ago
They do not. Those adjust the calendar, not the clock.
- kijin 5y ago
  A calendar is just a clock that measures longer durations of time.
  - user-the-name 5y ago
    Irrelevant in this context.
  - FabHK 5y ago
    But one of these adjustments aims to keep mid day at noon, while the other aims to keep solstice around 21 Dec. You could skip leap years and still have the sun up at noon, while your solstice date drifts away. Or, you could skip leak seconds and still have the solstice on 21 Dec, but have your noon drift away from mid day.
    - iso1631 5y ago
      very few locations have the sun directly above at 12 (based on a timezone offset from UTC), and just as many places have it directly above at 12 based on an offset from TAI The sun is overhead from Greenwich at 12:06 GMT today, it varies by about half an hour from 1143 to 1214 through the year (ignoring daylight saving) I'm not sure if varying from 1150 to 1221 would be any better. Even after a minute of leap seconds (say 100 years) the point where the "sun is overhead at 12:00:00" point for points at UK/Ireland latitude would have moved about 10 miles from its current position. in a few millenia the timezone would be wrong, but easilly corrected by either skipping a "spring forward" or "fall back" time.
throw0101a 5y ago
> Yeah, we already do the Feb 29 thing every 4 years. Except it's not every four years. It's every four years, but it is skipped if the year is divisible by 100… but not skipped if it is also divisible by 400—which ended up biting people in 2000 which was a leap year: * https://slate.com/technology/2016/02/the-math-behind-leap-years.html https://slate.com/technology/2016/02/the-math-behind-leap-ye...
- JadeNB 5y ago
  > > Yeah, we already do the Feb 29 thing every 4 years. > Except it's not every four years. > It's every four years, but it is skipped if the year is divisible by 100… but not skipped if it is also divisible by 400—which ended up biting people in 2000 which was a leap year …. Unless they edited, that's exactly what your parent said, after you cut off the quote: > Yeah, we already do the Feb 29 thing every 4 years. We make exceptions to that rule every 100 years, and an exception to the exception every 400 years.

throw0101a 5y ago

> Large parts of the world shift civil time by an hour twice a year. Yes, and how many things break every time this common thing occurs? Or every four years when February 29 rears its ugly head. And these are code paths that should be well tested because of their frequency.

iso1631 5y ago
POint is we can cope with the sun directly overhead at 14:20 (as it is today in Madrid), or at 11:20 (as it is in Warsaw in November) A drift of a minute over a lifetime makes no difference. We should just use TAI (with timezone offsets) for general time and be done with it. Even today UT1 is widely different to UTC (183ms), so it's not like using UTC is accurate. Why is 183ms an acceptable difference (no leap milliseconds), a couple of hours (timezone sizes), one hour (DST), but we have to correct for 40 seconds each century?