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Ask HN: Are systems ready for the first negative leap second?

Asmod4n · 2 days ago

It’s been 10 years since we had the last leap second and it looks like we will get the first negative one soonish. Are systems ready for that?

4 comments

  • d00d0ff000 · 2 days ago

    NTP.

    By any other standard, most manually set clocks are up to a full minute off all the time.

    • subscribed · 1 days ago

      Yeah, but we're thinking of systems where nanoseconds matter.

      MiFID 2 alone forces sub-μs precision. Million times less than the leap 1 second.

      NTP minute away is good for displaying date on the workstation, not for many of the devices that are critical to the modern world.

      • cyanydeez · 1 days ago

        dont most systems that rely on sharp timing simply manage it themselves.

        • subscribed · 1 days ago

          Yesno.

          Sure they have their own time servers fed from the GPS, but they need to be _accurate_ in relation to the world.

          But timestamps used by companies forced to use very accurate timing must be synchronised to UTC.

    • wmf · 2 days ago

      Systems are absolutely not ready. Leap seconds are a bad idea and negative leap seconds are worse. Just don't do it and let the drift cancel out.

      • toast0 · 1 days ago

        negative leap seconds aren't too bad. jumping forward a second won't lead to a time loop like jumping back did on several systems (some twice!)

        • yen223 · 1 days ago

          The brilliant thing about the smear is that it distributes the new second across each second of the day, so that each second differed by 1/86400 seconds, well within the margin of error for NTP.

          As far as the computers were concerned, nothing was different.

          • toast0 · 1 days ago

            The less brilliant thing about the smear is that if your ntpd syncs from smeared and unsmeared servers, the results aren't great.

            It would have been better if they would have kept the time on the wire accurate or added mandatory protocol stuff to avoid confusing things for ntpds configured to different leap second handling.

        • al_borland · 1 days ago

          If we have positive and negative leap seconds, why are we doing anything at all? 1 second forward, just to go 1 second back 10 years later…

          • yen223 · 1 days ago

            I don't think we can predict ahead of time whether we'll need a leap second or not

            If the question is "why bother syncing time to Earth's orbit around the sun at all", I don't have a good answer for that except at this point, it's tradition.