Birbla

Discussion summary

No leap second will be added at the end of December 2026, and discussions are ongoing about replacing leap seconds with leap hours. The decision depends on Earth's rotation, and systems like Spanner are unaffected by these irregular adjustments.

What the discussion says

  • Leap seconds are based on Earth's rotation and are not on a fixed schedule.
  • There is consideration to replace leap seconds with leap hours.
  • Decisions are made about 6 months in advance, depending on Earth's measurements.
“They're not adding a leap second this year, possibly not next year either.”
— ChrisArchitect
“Leap seconds depend on Earth's rotation, not a fixed calendar schedule.”
— metalliqaz

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  • Hacker News
  • They should have a global holiday to celebrate the people who maintain time/date related code in OS kernels that keeps the world from imploding.
    by t1234s
  • Lol. Exactly!
    by radomir_cernoch
  • Lol the Kernel is "easy" it's userspace and distributed systems that are a b*tch
    by raverbashing
  • They're cool people but like it doesn't stop the world from imploding. Most of all of our code is full of trivial bugs and edge cases and most people don't mind too much. Certainly no one cares about leap seconds, they hardly even notice DST or leap days
    by mtoner23
  • I like the argument that we should have 12 months that are exactly 30 days long, and then merge whatever is left into a single timeless holiday.
    by ortusdux
  • As one HN comment said years ago: I feel leap seconds have always lived in the wrong abstraction layer.

    They should live in the same abstraction layer that does leap days and daylight savings: the time zones.

    by returningfory2
  • That would create much more chaos, because every region autonomously decides on its timezone(s). You'd have different countries and/or timezones using different leap second counts.
    by layer8
  • Yes! I yearn for the day when central daylight savings time is 1:00:00:36 behind eastern time, but standard central time remains offset by 1 hour exactly (except for leap years, which are obviously 1:00:00:36 offset all year round).
    by clickety_clack
  • god that would be awful. Can you imagine time zones being one second off from each other. Or two or three? ah yes, india is GMT+4:30:03, where europe is GMT+0:59:58
    by RugnirViking
  • The changes in Earth's rotational speed that leap seconds help account for affect the whole globe. Why shouldn't the effects be noted in the global time standard?
    by stvltvs
  • Leap days, February 29th, are not at the level of time zones. Different time zones do not disagree as to when March 1st will occurs immediately after February 28th.
    by thwarted
  • The real Time Variance Authority
    by dodoisdodo
  • > The difference between Coordinated Universal Time UTC and the International Atomic Time TAI is :

    >

    > from 2017 January 1, 0h UTC, until further notice : UTC-TAI = -37s

    This means the atomic clock is behind the solar clock by 37 seconds? I also don’t understand the reference to 2017.

    by exegete
  • > I also don’t understand the reference to 2017.

    My guess is that is when they last changed the offset, so the -37s has been in effect since then.

    by doctoboggan
  • Apparently December 2016 was the last time a leap second was inserted, at least that's what Wikipedia says:

    https://en.wikipedia.org/wiki/Leap_second

    by flohofwoe
  • > This means the atomic clock is behind the solar clock by 37 seconds?

    If anything, it's the other way around.

    A UTC day is defined as exactly 86400 SI seconds. But an actual mean solar day is a few milliseconds longer (although the difference is not constant due to irregularities in the Earth's rotation--but the average difference is expected to slowly increase over time). SI seconds are counted by atomic clocks, so UTC advances its day by one every 86400 atomic clock seconds.

    But a solar clock that advances its day by one every time the mean sun reaches noon (it has to be the mean sun because the rate at which the actual sun moves across the sky varies over the course of a year, we need to look at the average) will advance its day a few milliseconds later than UTC does. Or, to put it another way, each time period that the solar clock says is exactly 86400 seconds, is a few milliseconds longer according to the atomic clock.

    As this happens day after day, the difference accumulates, and when it gets close to being a full second, a leap second gets inserted into UTC, so that one of its days is 86401 seconds long instead of 86400. The reason for this is that UTC is not just counting atomic clock time; it also has to stay in sync with where the sun is in the sky since so many human activities are tied to that. And we humans have defined "in sync with the sun" to be "within a second of the average sun". In other words, we want UTC noon to be within a second of mean solar noon on the prime meridian.

    So the 37 seconds is how far mean solar noon would be behind UTC noon, if we didn't use leap seconds--at UTC noon, the mean sun would be 37 seconds short of actually crossing the prime meridian in the sky.

    by pdonis
  • Hear me out. We can just mount jet engines along the equator and rotate them 180 to gain or lose time. And then connect them to my snooze button.
    by delichon
  • No, jet engines push against the atmosphere and the atmosphere is a part of the earth
    by Perz1val
  • It would appear that this has worked as they haven't had to insert leap seconds for quite a while.
    by Polizeiposaune
  • I feel like we can all just jump at the same time. I mean, we only need a second or two, right?
    by flippyhead
  • The problem is future societies harvesting the engines for interstellar probes. This problem has been discussed in a series of books by Larry Niven.
    by gumby
  • You could actually move very large quantities of water around and probably have a measurable impact. Like draining the California central valley aquifer.
    by s0rce
  • Wouldn't it just be easier to have Superman fly around the planet a bunch of times really fast to do the same thing? Then you wouldn't have to worry about having to deal with all of that engine maintenance.
    by dylan604
  • What happens to systems such as Spanner under these circumstances?

    Is it a headache or a non-issue

    by srean
  • Leap seconds are not added on a regular schedule like leap days, they depend on physical measurements of Earth. So high reliability systems with comprehensive timekeeping would not be perturbed by these choices, I would think.
    by metalliqaz
  • It’s a huge problem. The most common approach to address it is called smearing; the duration of each second for a 24 hour period ahead of the “leap” is adjusted. For strict ordering systems this works as each device maintains time sync with the global clock, the duration of a clock cycle is just slightly different. I think this was in the original Spanner paper, actually.

    Some rare systems use monotonic oscillator seconds and ignore the earth rotation second, but if you ever have to translate those to real time, you get an accumulating disaster over time and it’s generally regarded as not a good idea.

    by bri3d
  • If the UTC-TAI offset remains at -37s, then it also means the UTC-GPS offset remains at -18s. TAI and GPS have a constant 19s offset from each system.
    by KboPAacDA3
  • "To authorities responsible for the measurement and distribution of time" is just the best preamble ever.
    by bombcar
  • Planetary Defense Officer [1]

    [1] https://en.wikipedia.org/wiki/Planetary_Defense_Coordination...

    by danbruc
  • They should call themselves Time Lords
    by srdjanr