5 ms·

Why time may be running out for the leap second

19 points by edward 11y ago

nuxi7 11y ago
We should abolish DST while we are at it.
- ars 11y ago
  Yes we should, but it has nothing to do with this. DST is a local thing (state/province level), leap seconds are worldwide.
- vacri 11y ago
  I like having more sun-filled evening time.
  - throwaway7767 11y ago
    I think the idea is that we'd achieve the same effect by changing working hours. There's nothing sacred about 9-5. If you're dealing with people in different timezones, you need to know the offset of your timezones, and take DST into account. If this were changed, you'd need to know the offset of your timezones, and take local working hours into account. The benefit is not having to upgrade all the numerous specialised systems that may or may not be supported anymore every time a politician decides to change the clock. Having to throw out or hack around timekeeping problems with outdated-but-working embedded equipment carries costs. (This discussion is of course completely tangential to the article)
HappyTypist 11y ago
Perhaps we could adjust leap seconds once every 10 or 15 years. A 5 second change is unlikely to be disruptive if there is a common, semirare schedule.
- ars 11y ago
  That would be worse since most likely every single machine will fail - if it's not common no one will think to test or implement it. And a many-second jump is harder for the computer to handle smoothly, especially if it's a backward jump.
  - kqr 11y ago
    It's not a backward jump – you just let the clock run a bit slower for a minute, or an hour, or whatever. Smearing the second out works for 99% of people/computers, and when it doesn't you probably have much bigger problems keeping your clocks in sync anyway, so you should be able to handle a few leap seconds too.
kozak 11y ago
So they want to switch to what would be to de facto a non-fixed prime meridian (from time counting point of view) just because developers of time-critical systems are too lazy to use TAI or GPS time for internal time calculations...
- phicoh 11y ago
  At least for me the problem is that leap seconds are unpredictable. How many seconds are there until January 1st 2020? We don't know, nobody knows. You can only know for sure in 2019. That's bad, that's really bad. Performing internal calculations in TAI doesn't help if conversion between UTC and TAI is undefined for dates more than a year in the future. Another way to fix the issue would be to define predictable leap seconds, just like leap years are predictable. But I'd like to see them go. Nobody looks up to the sky and says "the sun is getting later and later". Half of the year most countries are far from solar time anyhow. Do I care where the sun is relative to some arbitrary line in England? No.
  - ars 11y ago
    I do like knowing when sunset is though. A second or two won't matter, but after some decades all the formulas for calculating sunset time will be wrong.
    - phicoh 11y ago
      During one lifetime, you will see (at the current rate) about 60 leap seconds. Do you really notice if the sunset time is off by one minute? Note that moving 30 km (or 20 miles) east or west also changes the sunset by one minute.
      - eru 11y ago
        > Note that moving 30 km (or 20 miles) east or west also changes the sunset by one minute. Depending on how close to the poles / equator you are, and probably also time of the year.
      - 11y ago
wodenokoto 11y ago
I don't really get what the proposed alternative is here. To just let the time of day drift away from the time on the clock? Then way not abolish leap years as well?
- hugh4 11y ago
  Just let it drift, yes, I assume. Then maybe in a few thousand years when we're a full hour out we can think about having a leap hour. Abolishing leap years, on the other hand, would cause the calendar to shift relative to the seasons by a notable amount during your lifetime.
  - kqr 11y ago
    > Then maybe in a few thousand years when we're a full hour out we can think about having a leap hour. If we even care, at that point. We might well have switched time keeping systems several times by then, seen massive improvements in artificial lighting and heating and such. I think that's the general idea of "what's the point of leap seconds". By the time they actually matter, we're not sure they matter anymore.
- nitwit005 11y ago
  Leap years run into a similar issue that the ratio of days to years is changing as well. Our current algorithm will eventually be off. No one cares because the people doing time standards will be long dead. And arguably the situation is similar for leap seconds as well. No one cares because of how far out substantial drift is. By the time it adds up to an hour, people will be used to it, or just shift their timezones (which happens all the time).
- phphphph 11y ago
  Leap years are regular, leap seconds are not. Skipping leap day would be earlier and more obviously noticable than skipping leap seconds.
- cbd1984 11y ago
  > Then way not abolish leap years as well? Religion. For example, the various Christian groups want to keep Easter at the Correct Time each year, and the leap year is part of the complex calculations they use to accomplish that. https://en.wikipedia.org/wiki/Computus https://en.wikipedia.org/wiki/Computus It really is a bit involved. I suppose they could redo everything to accommodate a calendar without a leap day, but the Julian to Gregorian update was divisive enough, and you really expect them to go through all that again so soon? More to the point, calendars are more deeply embedded in the culture than things like TAI and UTC and so on. Changing a calendar is a maybe-once-in-a-millennia event.
drallison 11y ago
The very concept of a leap second is flawed. Given two times (say T1 and T2) we need to be able to compute, accurately, the elapsed time. Time series data becomes difficult to interpret accurately.
upofadown 11y ago
This seems like a natural progression to me. When the rotation of the earth was the most accurate period available then it made sense to use that as a reference. Now it is not and it doesn't. I think that in the future people will just use UT for anything where people have to coordinate activities. We can have a separate time scale for things we want to coordinate relative to sunrise and sunset. This scale will be able to be completely accurate based on location so we would abolish stupid stuff line time zones and DST. The result will be much simpler.

19 points by edward 11y ago

nuxi7 11y ago

We should abolish DST while we are at it.

ars 11y ago
Yes we should, but it has nothing to do with this. DST is a local thing (state/province level), leap seconds are worldwide.
vacri 11y ago
I like having more sun-filled evening time.
- throwaway7767 11y ago
  I think the idea is that we'd achieve the same effect by changing working hours. There's nothing sacred about 9-5. If you're dealing with people in different timezones, you need to know the offset of your timezones, and take DST into account. If this were changed, you'd need to know the offset of your timezones, and take local working hours into account. The benefit is not having to upgrade all the numerous specialised systems that may or may not be supported anymore every time a politician decides to change the clock. Having to throw out or hack around timekeeping problems with outdated-but-working embedded equipment carries costs. (This discussion is of course completely tangential to the article)

HappyTypist 11y ago

Perhaps we could adjust leap seconds once every 10 or 15 years. A 5 second change is unlikely to be disruptive if there is a common, semirare schedule.

ars 11y ago
That would be worse since most likely every single machine will fail - if it's not common no one will think to test or implement it. And a many-second jump is harder for the computer to handle smoothly, especially if it's a backward jump.
- kqr 11y ago
  It's not a backward jump – you just let the clock run a bit slower for a minute, or an hour, or whatever. Smearing the second out works for 99% of people/computers, and when it doesn't you probably have much bigger problems keeping your clocks in sync anyway, so you should be able to handle a few leap seconds too.

kozak 11y ago

So they want to switch to what would be to de facto a non-fixed prime meridian (from time counting point of view) just because developers of time-critical systems are too lazy to use TAI or GPS time for internal time calculations...

phicoh 11y ago
At least for me the problem is that leap seconds are unpredictable. How many seconds are there until January 1st 2020? We don't know, nobody knows. You can only know for sure in 2019. That's bad, that's really bad. Performing internal calculations in TAI doesn't help if conversion between UTC and TAI is undefined for dates more than a year in the future. Another way to fix the issue would be to define predictable leap seconds, just like leap years are predictable. But I'd like to see them go. Nobody looks up to the sky and says "the sun is getting later and later". Half of the year most countries are far from solar time anyhow. Do I care where the sun is relative to some arbitrary line in England? No.
- ars 11y ago
  I do like knowing when sunset is though. A second or two won't matter, but after some decades all the formulas for calculating sunset time will be wrong.
  - phicoh 11y ago
    During one lifetime, you will see (at the current rate) about 60 leap seconds. Do you really notice if the sunset time is off by one minute? Note that moving 30 km (or 20 miles) east or west also changes the sunset by one minute.
    - eru 11y ago
      > Note that moving 30 km (or 20 miles) east or west also changes the sunset by one minute. Depending on how close to the poles / equator you are, and probably also time of the year.
    - 11y ago

wodenokoto 11y ago

I don't really get what the proposed alternative is here. To just let the time of day drift away from the time on the clock? Then way not abolish leap years as well?

hugh4 11y ago
Just let it drift, yes, I assume. Then maybe in a few thousand years when we're a full hour out we can think about having a leap hour. Abolishing leap years, on the other hand, would cause the calendar to shift relative to the seasons by a notable amount during your lifetime.
- kqr 11y ago
  > Then maybe in a few thousand years when we're a full hour out we can think about having a leap hour. If we even care, at that point. We might well have switched time keeping systems several times by then, seen massive improvements in artificial lighting and heating and such. I think that's the general idea of "what's the point of leap seconds". By the time they actually matter, we're not sure they matter anymore.
nitwit005 11y ago
Leap years run into a similar issue that the ratio of days to years is changing as well. Our current algorithm will eventually be off. No one cares because the people doing time standards will be long dead. And arguably the situation is similar for leap seconds as well. No one cares because of how far out substantial drift is. By the time it adds up to an hour, people will be used to it, or just shift their timezones (which happens all the time).
phphphph 11y ago
Leap years are regular, leap seconds are not. Skipping leap day would be earlier and more obviously noticable than skipping leap seconds.
cbd1984 11y ago
> Then way not abolish leap years as well? Religion. For example, the various Christian groups want to keep Easter at the Correct Time each year, and the leap year is part of the complex calculations they use to accomplish that. https://en.wikipedia.org/wiki/Computus https://en.wikipedia.org/wiki/Computus It really is a bit involved. I suppose they could redo everything to accommodate a calendar without a leap day, but the Julian to Gregorian update was divisive enough, and you really expect them to go through all that again so soon? More to the point, calendars are more deeply embedded in the culture than things like TAI and UTC and so on. Changing a calendar is a maybe-once-in-a-millennia event.

drallison 11y ago

The very concept of a leap second is flawed. Given two times (say T1 and T2) we need to be able to compute, accurately, the elapsed time. Time series data becomes difficult to interpret accurately.

upofadown 11y ago

This seems like a natural progression to me. When the rotation of the earth was the most accurate period available then it made sense to use that as a reference. Now it is not and it doesn't. I think that in the future people will just use UT for anything where people have to coordinate activities. We can have a separate time scale for things we want to coordinate relative to sunrise and sunset. This scale will be able to be completely accurate based on location so we would abolish stupid stuff line time zones and DST. The result will be much simpler.