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Google's New Public NTP Servers Provide Smeared Time (googleblog.com)

Posted by msmash on from the fixing-things dept.

Google says it has built support for the leap second into the time servers that regulate all Google services. An anonymous reader shares a blogpost by Google:No commonly used operating system is able to handle a minute with 61 seconds, and trying to special-case the leap second has caused many problems in the past. Instead of adding a single extra second to the end of the day, we'll run the clocks 0.0014% slower across the ten hours before and ten hours after the leap second, and "smear" the extra second across these twenty hours. For timekeeping purposes, December 31 will seem like any other day. All Google services, including all APIs, will be synchronized on smeared time, as described above. You'll also get smeared time for virtual machines on Compute Engine if you follow our recommended settings. You can use non-Google NTP servers if you don't want your instances to use the leap smear, but don't mix smearing and non-smearing time servers.

2 of 179 comments (clear)

  1. Not new, just a holiday reminder PSA by Anonymous Coward · · Score: 5, Informative

    Google has been smearing leap seconds over NTP since 2011. This is a public reminder that Google NTP will be serving smear seconds because there is one coming.

  2. Re:Falsehoods Developers Believe About Time by heypete · · Score: 4, Informative

    Because that's how they did it before and they consider it "safer" in the context of not making uneccessary changes this soon to the leap second. In the future they plan to do it 24 hours in advance:

    Although we decided it would be safest for Google's infrastructure to handle the 2016 leap second using a 20-hour smear, the same way we handled the leap seconds in 2012 and 2015, this is not the only smear that works well. Many organizations use smeared clocks, and it would be helpful if the smears were the same. After all, the purpose of clocks is to read the same time in different places.

    We would like to propose to the community, as the best practice for leap seconds in the future, a 24-hour linear smear from noon to noon UTC. We plan to use this smear starting from leap second #38, which is likely to be in 2018.

    Source: https://developers.google.com/time/smear.