9 ms·

> The complexity goes up tremendously if some condition is rarely encountered: eg leap second. This means it gets pushed to a "corner case" and tested more ligh

> The complexity goes up tremendously if some condition is rarely encountered: eg leap second. This means it gets pushed to a "corner case" and tested more lightly and more rarely. There is some talk of eliminating the leap second, which would over time have the Earth and sun diverge with regards to noon and such. One 'answer' to this concern is to have a 'leap hour' or something in the future (some future generation's problem, not ours): but given that people can't even get February 29th correct now, and it happens regularly, I don't see how a one-off event would be made to work. It'd be a huge coördination problem. Just look at the introduction of the Gregorian calendar: it was slightly off since the time of Julius Caesar, but that minor error added up over time, to the point that to get the equinoxes/solstices back to where they 'should' be 10 days had to be removed with the Gregorian calendar. And because of politics (or a religious flavour) it took a long while for everyone to get on the same page.

tialaramex 7mo ago
The calendar adjustments are because the planet's constant orbital period isn't a whole number of days. The leap seconds were an attempt to have wall clock time map to the planet's rotational angle consistently despite the problem that the planet's spin varies unpredictably. Yes the "leap hour" is a legal fiction of course. In reality in the event anybody cares about this in the distant future they will make the kind of "drastic" changes you've probably experienced twice a year for your whole life and barely noticed... More likely because the drift is so incredibly slow they won't change anything.
- throw0101c 7mo ago
  So lunar tidal forces are slowing the rotation, but (recently?) Earth mantle/core is causing a speed up, but climate change and melting ice is contributing to the slow down side: * https://www.scientificamerican.com/article/leap-seconds-may-be-abandoned-by-the-worlds-timekeepers/ https://www.scientificamerican.com/article/leap-seconds-may-... * https://scripps.ucsd.edu/news/global-warming-influencing-global-timekeeping https://scripps.ucsd.edu/news/global-warming-influencing-glo... The general trend is slowing down. Apparently (?) once the day gets to be 24h+0.001sec (+1 millisecond), a leap second would occur about every 1000 days; then when it becomes 24h+0.002sec, a leap second would occur about every 500 days; when it reaches 24h+0.003sec, a leap second would occur about every year; etc.
- deleted 7mo ago
  [deleted]
deleted 7mo ago
[deleted]
amenghra 7mo ago
IMHO the correct way to handle leap seconds would have been at the same layer as timezones, i.e. a display-only thing. Timezone databases are regularly updated, you push out leap second updates there. In the worst case, people's clocks are off by one second but all the underlying timing logic doesn't crash.
- Polizeiposaune 7mo ago
  I fully expect in such a regime, people would be complaining about how the leap second insertion caused their recurring meeting to shift from 9am to 8:59:59
- Palomides 7mo ago
  you can use TAI (international atomic time, basically UTC without leap seconds) if you want to be serious about it I'm a fan but it's rare for anyone else to agree!
  - phicoh 7mo ago
    The problem with TAI is that the rest of the world uses UTC. So you can use TAI on a small island and then you have to convert to and from UTC. My hobby kernel is based on TAI internally. And it constantly converts to and from UTC.
    - adrian_b 7mo ago
      You do not use TAI to communicate with the rest of the world, except for certain special purposes. As you say, what the computer should maintain internally and for communication with other computers, not with humans, is only true time and not other quantities, like the angles between Earth, Sun and stars. Only TAI is true time, while "universal time" is an angle and "universal time coordinated" (UTC) and its derivatives are some weird hybrid quantities that can be computed from times and angles. The conversions between true time and various kinds of official times used by humans are very complex and they should be handled in a single place, not in various places that may handle time zones and discrepancies between UTC and TAI and various other "times", e.g. UT2, UT1 etc.
wmf 7mo ago
We had a leap hour yesterday...
- throw0101d 7mo ago
  > We had a leap hour yesterday... Prescheduled. Now tell everyone we're having one June 30, 2029, and see how things go.
  - wmf 7mo ago
    If we eliminate leap seconds, we'll need a leap hour in ~500 years. It could be announced 50 years in advance.
    - throw0101c 7mo ago
      > It could be announced 50 years in advance. Which is about how long it took for folks to switch from the Julian to the Gregorian calendar.
      - wmf 7mo ago
        In the US DST was changed in 2005 and the change went into effect in 2007.
      - tmp10423288442 7mo ago
        It took much longer than that, although to be fair the Catholic countries had switched in much sooner than 50 years.
zamadatix 7mo ago
Leap seconds have so many problems beyond the time adjustment. It's a small/odd enough adjustment interval that there are wildly different approaches like leap smears. On top of being so small, it's rare enough (~every 2 years), depending on how a system is used, lack of proper handling might not be obviously apparent or lack of obvious problem in one implementation ignoring it may lead to lack of care in another implementation which would have a problem ignoring it. Leap hour replaces all of that with what is more or less equivalent to a change in DST rules (except for more time zones at once). DST changes don't go perfect either by any means... but we do them regularly enough without the world crashing down that doing an additional shift change of an extra hour every 5000 years is almost certainly less hassle and breakage than the leap second approach breaking things every ~2 years.
- phicoh 7mo ago
  It is way more easy to let UTC (without leap seconds) just drift away from the zero meridian and move countries to different time zones when convenient. We mess around with daylight savings time often enough that nobody will notice if we have change local time every couple of thousand years.
- throw0101d 7mo ago
  DST changes are pre-scheduled. Throwing a random hour in/out at (say) June 30, 2029 may be something else. Unless the jump is treated as a TZ change in tzdata?
  - recursivecaveat 7mo ago
    Yeah you treat it as a time zone change where every zone moves over (or every country moves to the adjacent zone maybe). You can schedule it N years in advance. It's definitely not 0 disruption, but it's very manageable. Regions change TZs or toggle DST frequently enough that we can handle it.
philwelch 7mo ago
> There is some talk of eliminating the leap second, which would over time have the Earth and sun diverge with regards to noon and such “Over time” really glosses over how much time it would take. In 500 years there might be half as much divergence between solar noon and 12:00pm as we intentionally inflict on ourselves with DST, or that France and Spain inflicted on themselves in the 1940’s so they could share a time zone with Germany. By the time anyone will even notice we will probably change time systems for other reasons anyway. It’s not even remotely comparable to the Julian/Gregorian issue, which dealt with leap days. Each day has 86400 seconds.
b112 7mo ago
If you think you're going to steal days off my life, you've got another thing coming buster!
euroderf 7mo ago
> There is some talk of eliminating the leap second, which would over time have the Earth and sun diverge with regards to noon and such. <rant> It won't happen on a human scale. So why oh why do we screw around with this moronic leap-second nonsense ? Oh dear, in the year 4000 noon will arrive three minutes earlier compared to now. So? </rant>
michaelt 7mo ago
> One 'answer' to this concern is to have a 'leap hour' or something in the future We've had 27 leapseconds in the last 54 years [1] - an average of 0.5 seconds per year. At that rate, solar time will drift by 60 seconds over the course of 120 years. Drifting by 10 minutes will take 1200 years. The leap hour will be in 7200 years, around year 9226. [1] https://en.wikipedia.org/wiki/Leap_second https://en.wikipedia.org/wiki/Leap_second
- throwup238 7mo ago
  > The leap hour will be in 7200 years, around year 9226. 7200 years ago the Neolithic revolution was still in full swing and many of the most famous megaliths like Stonehenge hadn’t even been built yet. The first real state, the Sumerian civilization, hadn’t formed yet in Mesopotamia. Personally, I’m very comfortable making this someone else’s problems 7200 years from now. If they’re still having basic coordination issues then it’s their own damn problem.
  - refulgentis 7mo ago
    "Basic" made me lol :)
  - vmilner 7mo ago
    "And so the Y10K problem was born"
    - IKnowComputer 7mo ago
      I’d better go brush up on my COBOL
      - tadfisher 7mo ago
        Programmer-Archaeologist will be quite a coveted position 300 gigaseconds from now.
    - caymanjim 7mo ago
      I just had a Y10K problem. Customer data was using 9999-12-31 23:59:59 as a placeholder value, and our app crashed converting from the customer's timezone to UTC. I learned that Python datetime can't handle Y10K.
clickety_clack 7mo ago
In British Colombia they’re locking into daylight savings time, so I think it’s safe to say that people aren’t really bothered by solar accuracy.
- WorldMaker 7mo ago
  I believe Vancouver is west enough in its time zone that Daylight time is going to be closer to Solar Noon in Vancouver (plus about 15 minutes? I haven't done the exact math) than Standard time was (minus about 45 minutes?). Vancouver is the economic heart of British Columbia and near enough to the centroid of BC's population that BC may have made the best choice they could for solar accuracy for the majority of the population.
TurdF3rguson 7mo ago
>There is some talk of eliminating the leap second The concern, of course, is that some universes eliminating them while others don't can puts us out of sync. This creates a wobble that could potentially throw us out of Hilbert space.
- nstents 7mo ago
  [dead]
cesarb 7mo ago
> One 'answer' to this concern is to have a 'leap hour' or something in the future (some future generation's problem, not ours) A simpler solution: we already have an offset between local time and coordinated time, just change that offset. So, for instance, Brasília Time, which is currently UTC-03, would become UTC-02 or UTC-04, depending on which way the change went.
adrian_b 7mo ago
Unfortunately, the Gregorian calendar has not restored the time of Julius Caesar, but the time of the First Council of Nicaea (325 AD), when the rule about how to compute the date of the Easter was established. For the time of Julius Caesar, about 3 more days would have been needed, which would have made the Christmas coincident with the Winter Solstice, and which would have made much more sense.
thaumasiotes 7mo ago
> to the point that to get the equinoxes/solstices back to where they 'should' be 10 days had to be removed with the Gregorian calendar Note that the equinoxes and solstices are officially supposed to be on the 25th. By the time of Julius Caesar, that had diverged, but the divergence in reality made no impact on the date of the official solstice. The Gregorian calendar could easily have put the solstices back on the 25th, but chose not to.
- adrian_b 7mo ago
  By the time of Julius Caesar, the solstices were on the 25th, which is the reason why Christmas is celebrated on that day. The Gregorian calendar has not restored the time of Julius Caesar, but the time of the First Council of Nicaea (325 AD), when the rule about how to compute the date of the Easter was established. From the time of Julius Caesar to 325 AD, more than 3 days of drift had accumulated, so the Gregorian calendar would have required 13 or 14 days of correction. When many countries transitioned to the Gregorian calendar much later, they had to add additional correction days to the initial 10-day difference, about 1 day per century.
  - thaumasiotes 7mo ago
    > By the time of Julius Caesar, the solstices were on the 25th That is false. See https://kiwihellenist.blogspot.com/2022/05/julian-calendar.html https://kiwihellenist.blogspot.com/2022/05/julian-calendar.h... , or "Digression #2: why do Roman writers report the date of the solstice as 25 December?" at https://kiwihellenist.blogspot.com/2015/12/christmas-and-its-supposed-pagan-links.html https://kiwihellenist.blogspot.com/2015/12/christmas-and-its... . Solstices were on the 25th a few hundred years before the time of Julius Caesar. He did not even attempt to put them back there.

tialaramex 7mo ago

The calendar adjustments are because the planet's constant orbital period isn't a whole number of days. The leap seconds were an attempt to have wall clock time map to the planet's rotational angle consistently despite the problem that the planet's spin varies unpredictably. Yes the "leap hour" is a legal fiction of course. In reality in the event anybody cares about this in the distant future they will make the kind of "drastic" changes you've probably experienced twice a year for your whole life and barely noticed... More likely because the drift is so incredibly slow they won't change anything.

throw0101c 7mo ago
So lunar tidal forces are slowing the rotation, but (recently?) Earth mantle/core is causing a speed up, but climate change and melting ice is contributing to the slow down side: * https://www.scientificamerican.com/article/leap-seconds-may-be-abandoned-by-the-worlds-timekeepers/ https://www.scientificamerican.com/article/leap-seconds-may-... * https://scripps.ucsd.edu/news/global-warming-influencing-global-timekeeping https://scripps.ucsd.edu/news/global-warming-influencing-glo... The general trend is slowing down. Apparently (?) once the day gets to be 24h+0.001sec (+1 millisecond), a leap second would occur about every 1000 days; then when it becomes 24h+0.002sec, a leap second would occur about every 500 days; when it reaches 24h+0.003sec, a leap second would occur about every year; etc.
deleted 7mo ago
[deleted]

deleted 7mo ago

[deleted]

amenghra 7mo ago

IMHO the correct way to handle leap seconds would have been at the same layer as timezones, i.e. a display-only thing. Timezone databases are regularly updated, you push out leap second updates there. In the worst case, people's clocks are off by one second but all the underlying timing logic doesn't crash.

Polizeiposaune 7mo ago
I fully expect in such a regime, people would be complaining about how the leap second insertion caused their recurring meeting to shift from 9am to 8:59:59
Palomides 7mo ago
you can use TAI (international atomic time, basically UTC without leap seconds) if you want to be serious about it I'm a fan but it's rare for anyone else to agree!
- phicoh 7mo ago
  The problem with TAI is that the rest of the world uses UTC. So you can use TAI on a small island and then you have to convert to and from UTC. My hobby kernel is based on TAI internally. And it constantly converts to and from UTC.
  - adrian_b 7mo ago
    You do not use TAI to communicate with the rest of the world, except for certain special purposes. As you say, what the computer should maintain internally and for communication with other computers, not with humans, is only true time and not other quantities, like the angles between Earth, Sun and stars. Only TAI is true time, while "universal time" is an angle and "universal time coordinated" (UTC) and its derivatives are some weird hybrid quantities that can be computed from times and angles. The conversions between true time and various kinds of official times used by humans are very complex and they should be handled in a single place, not in various places that may handle time zones and discrepancies between UTC and TAI and various other "times", e.g. UT2, UT1 etc.

wmf 7mo ago

We had a leap hour yesterday...

throw0101d 7mo ago
> We had a leap hour yesterday... Prescheduled. Now tell everyone we're having one June 30, 2029, and see how things go.
- wmf 7mo ago
  If we eliminate leap seconds, we'll need a leap hour in ~500 years. It could be announced 50 years in advance.
  - throw0101c 7mo ago
    > It could be announced 50 years in advance. Which is about how long it took for folks to switch from the Julian to the Gregorian calendar.
    - wmf 7mo ago
      In the US DST was changed in 2005 and the change went into effect in 2007.
    - tmp10423288442 7mo ago
      It took much longer than that, although to be fair the Catholic countries had switched in much sooner than 50 years.

zamadatix 7mo ago

Leap seconds have so many problems beyond the time adjustment. It's a small/odd enough adjustment interval that there are wildly different approaches like leap smears. On top of being so small, it's rare enough (~every 2 years), depending on how a system is used, lack of proper handling might not be obviously apparent or lack of obvious problem in one implementation ignoring it may lead to lack of care in another implementation which would have a problem ignoring it. Leap hour replaces all of that with what is more or less equivalent to a change in DST rules (except for more time zones at once). DST changes don't go perfect either by any means... but we do them regularly enough without the world crashing down that doing an additional shift change of an extra hour every 5000 years is almost certainly less hassle and breakage than the leap second approach breaking things every ~2 years.

phicoh 7mo ago
It is way more easy to let UTC (without leap seconds) just drift away from the zero meridian and move countries to different time zones when convenient. We mess around with daylight savings time often enough that nobody will notice if we have change local time every couple of thousand years.
throw0101d 7mo ago
DST changes are pre-scheduled. Throwing a random hour in/out at (say) June 30, 2029 may be something else. Unless the jump is treated as a TZ change in tzdata?
- recursivecaveat 7mo ago
  Yeah you treat it as a time zone change where every zone moves over (or every country moves to the adjacent zone maybe). You can schedule it N years in advance. It's definitely not 0 disruption, but it's very manageable. Regions change TZs or toggle DST frequently enough that we can handle it.

philwelch 7mo ago

> There is some talk of eliminating the leap second, which would over time have the Earth and sun diverge with regards to noon and such “Over time” really glosses over how much time it would take. In 500 years there might be half as much divergence between solar noon and 12:00pm as we intentionally inflict on ourselves with DST, or that France and Spain inflicted on themselves in the 1940’s so they could share a time zone with Germany. By the time anyone will even notice we will probably change time systems for other reasons anyway. It’s not even remotely comparable to the Julian/Gregorian issue, which dealt with leap days. Each day has 86400 seconds.

b112 7mo ago

If you think you're going to steal days off my life, you've got another thing coming buster!

euroderf 7mo ago

> There is some talk of eliminating the leap second, which would over time have the Earth and sun diverge with regards to noon and such. <rant> It won't happen on a human scale. So why oh why do we screw around with this moronic leap-second nonsense ? Oh dear, in the year 4000 noon will arrive three minutes earlier compared to now. So? </rant>

michaelt 7mo ago

> One 'answer' to this concern is to have a 'leap hour' or something in the future We've had 27 leapseconds in the last 54 years [1] - an average of 0.5 seconds per year. At that rate, solar time will drift by 60 seconds over the course of 120 years. Drifting by 10 minutes will take 1200 years. The leap hour will be in 7200 years, around year 9226. [1] https://en.wikipedia.org/wiki/Leap_second https://en.wikipedia.org/wiki/Leap_second

throwup238 7mo ago
> The leap hour will be in 7200 years, around year 9226. 7200 years ago the Neolithic revolution was still in full swing and many of the most famous megaliths like Stonehenge hadn’t even been built yet. The first real state, the Sumerian civilization, hadn’t formed yet in Mesopotamia. Personally, I’m very comfortable making this someone else’s problems 7200 years from now. If they’re still having basic coordination issues then it’s their own damn problem.
- refulgentis 7mo ago
  "Basic" made me lol :)
- vmilner 7mo ago
  "And so the Y10K problem was born"
  - IKnowComputer 7mo ago
    I’d better go brush up on my COBOL
    - tadfisher 7mo ago
      Programmer-Archaeologist will be quite a coveted position 300 gigaseconds from now.
  - caymanjim 7mo ago
    I just had a Y10K problem. Customer data was using 9999-12-31 23:59:59 as a placeholder value, and our app crashed converting from the customer's timezone to UTC. I learned that Python datetime can't handle Y10K.

clickety_clack 7mo ago

In British Colombia they’re locking into daylight savings time, so I think it’s safe to say that people aren’t really bothered by solar accuracy.

WorldMaker 7mo ago
I believe Vancouver is west enough in its time zone that Daylight time is going to be closer to Solar Noon in Vancouver (plus about 15 minutes? I haven't done the exact math) than Standard time was (minus about 45 minutes?). Vancouver is the economic heart of British Columbia and near enough to the centroid of BC's population that BC may have made the best choice they could for solar accuracy for the majority of the population.

TurdF3rguson 7mo ago

>There is some talk of eliminating the leap second The concern, of course, is that some universes eliminating them while others don't can puts us out of sync. This creates a wobble that could potentially throw us out of Hilbert space.

nstents 7mo ago
[dead]

cesarb 7mo ago

> One 'answer' to this concern is to have a 'leap hour' or something in the future (some future generation's problem, not ours) A simpler solution: we already have an offset between local time and coordinated time, just change that offset. So, for instance, Brasília Time, which is currently UTC-03, would become UTC-02 or UTC-04, depending on which way the change went.

adrian_b 7mo ago

Unfortunately, the Gregorian calendar has not restored the time of Julius Caesar, but the time of the First Council of Nicaea (325 AD), when the rule about how to compute the date of the Easter was established. For the time of Julius Caesar, about 3 more days would have been needed, which would have made the Christmas coincident with the Winter Solstice, and which would have made much more sense.

thaumasiotes 7mo ago

> to the point that to get the equinoxes/solstices back to where they 'should' be 10 days had to be removed with the Gregorian calendar Note that the equinoxes and solstices are officially supposed to be on the 25th. By the time of Julius Caesar, that had diverged, but the divergence in reality made no impact on the date of the official solstice. The Gregorian calendar could easily have put the solstices back on the 25th, but chose not to.

adrian_b 7mo ago
By the time of Julius Caesar, the solstices were on the 25th, which is the reason why Christmas is celebrated on that day. The Gregorian calendar has not restored the time of Julius Caesar, but the time of the First Council of Nicaea (325 AD), when the rule about how to compute the date of the Easter was established. From the time of Julius Caesar to 325 AD, more than 3 days of drift had accumulated, so the Gregorian calendar would have required 13 or 14 days of correction. When many countries transitioned to the Gregorian calendar much later, they had to add additional correction days to the initial 10-day difference, about 1 day per century.
- thaumasiotes 7mo ago
  > By the time of Julius Caesar, the solstices were on the 25th That is false. See https://kiwihellenist.blogspot.com/2022/05/julian-calendar.html https://kiwihellenist.blogspot.com/2022/05/julian-calendar.h... , or "Digression #2: why do Roman writers report the date of the solstice as 25 December?" at https://kiwihellenist.blogspot.com/2015/12/christmas-and-its-supposed-pagan-links.html https://kiwihellenist.blogspot.com/2015/12/christmas-and-its... . Solstices were on the 25th a few hundred years before the time of Julius Caesar. He did not even attempt to put them back there.