Windows 10 Getting Support for Leap Seconds

Microsoft is bringing support for leap seconds — yes, that one extra second — to Windows, starting with Windows 10 Redstone 5 and Windows Server 2019. With the upcoming updates for Windows 10, Microsoft’s operating system now deals with leap seconds in a way that is incredibly accurate, UTC-compliant, and traceable.

Leap seconds typically occur every 18 months, resulting in one extra second. The extra leap second occurs to adjust with the earth’s slowed down rotation, and an extra second is added to UTC in order to keep it in-sync with mean solar time. To deal with the extra second more appropriately, Windows 10 will now display that extra second, instead of directly jumping to the next one, making it the world’s first OS to have full support for leap seconds. It’s quite difficult to explain in words, but the following GIF will help make it less confusing:

Right now, Windows 10 directly jumps from 16:59:59 to 17:00:00 without a leap second, but it will now include 16:59:60 when there is an actual leap second. That one extra second is quite important for time accuracy, especially with increased demand for higher accuracy time from government regulations, according to Microsoft. The company says it will not include an option for leap second smearing where the extra second would be split up into smaller units and added throughout the day as it will prevent the OS from meeting accuracy requirements.

Microsoft is delivering a number of other improvements in Windows Server 2019 to provide better time accuracy, including a new Precision Time Control, time synchronization method, and more. Microsoft has detailed all of the new improvements in a technical blog post here, and you can read about all the improvements coming with future versions of Windows 10 if you happen to care about such improvements.

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Conversation 17 comments

  • plettza

    18 July, 2018 - 4:06 pm

    <p>I wonder what Event Viewer would read when an even occurs precisely at the 60 second mark.</p>

  • CaedenV

    18 July, 2018 - 4:18 pm

    <p>I am curious as to why we need this… People who care about acurate time set up an NTP server and push time to everyone. The time is never wrong for more than 5 minutes.</p>

    • jgraebner

      Premium Member
      18 July, 2018 - 4:32 pm

      <blockquote><em><a href="#293453">In reply to CaedenV:</a></em></blockquote><p>The article mentioned government regulations. This might be important on computers that are dealing with secure tasks that wouldn't allow a network connection. </p><p><br></p><p>I could also see where inaccuracies between updates from an NTP server could be a big deal for certain scientific applications.</p>

    • MikeGalos

      18 July, 2018 - 9:35 pm

      <blockquote><a href="#293453"><em>In reply to CaedenV:</em></a></blockquote><p>Because for some people other than you being wrong for a few seconds for 5 minutes is horribly damaging. </p>

      • Jeffsters

        18 July, 2018 - 9:58 pm

        <blockquote><a href="#293558"><em>In reply to MikeGalos:</em></a></blockquote><p>Lol…on servers and routers perhaps but desktops? LOL! Lots of users, now and for years, neglect to have their machines set to auto update using npt and it doesn’t deem to be “horribly damaging”. I guess paraphrasing Spock in the 2009 film…”MikeGalos <span style="background-color: rgb(246, 246, 245); color: rgb(51, 51, 51);">inferred that universe-ending paradoxes would ensue should leap second not be autoset”.</span></p>

        • Rickard Eriksson

          19 July, 2018 - 4:23 am

          <blockquote><a href="#293563"><em>In reply to Jeffsters:</em></a></blockquote><p>Then they are not doing work that are time critical then. There are research etc done that are not demanding enough to be run on servers yet have to be exact and then leap seconds could throw calculations off. </p>

          • MikeGalos

            19 July, 2018 - 12:07 pm

            <blockquote><a href="#293595"><em>In reply to Rickard Eriksson:</em></a></blockquote><p>A "server" is designed for specific functionality like serving files or serving shared resources. It's not the word for "serious computer".</p><p><br></p>

        • MikeGalos

          19 July, 2018 - 12:06 pm

          <blockquote><a href="#293563"><em>In reply to Jeffsters:</em></a></blockquote><p>Yes. On desktops. You see, not everybody is in an office filing sales reports. Some people use their desktop systems for things like scientific computing and some systems use a desktop computer to run process automation, etc.</p><p>As I said, to CaedenV, there are people other than you.</p>

  • chrisrut

    Premium Member
    18 July, 2018 - 4:33 pm

    <p>Ooooohhhh, leap seconds. My clock runneth over…</p>

    • AnOldAmigaUser

      Premium Member
      18 July, 2018 - 9:33 pm

      <blockquote><a href="#293460"><em>In reply to chrisrut:</em></a></blockquote><p>But only a little…</p>

    • jrswarr

      Premium Member
      19 July, 2018 - 5:47 am

      <p>Brings new meaning to "Hey – got a sec?"</p>

  • slartybartmark

    18 July, 2018 - 4:49 pm

    <p>Can we ask MS to put the people involved in level of detail on the monthly patch testing? </p><p><br></p><p><em>(one asks innocently as one is re-applying patches to Exchange and several other servers after the patches were hosed this month (again) and reissued)</em></p>

  • MikeGalos

    18 July, 2018 - 9:36 pm

    <p>Fantastic. That's actually a harder problem than it looks and needed standards compliance. </p><p><br></p><p>Now, the question is which other operating systems don't have this feature and when will they catch up.</p>

  • BoItmanLives

    19 July, 2018 - 12:58 am

    <p>How about a leap telemetry off switch </p>

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