[tz] Google public NTP servers to 'smear' leap seconds.

John Hawkinson jhawk at MIT.EDU
Sun Dec 4 22:24:50 UTC 2016

As we have learned the hard way, words put into the tz distribution
matter, and sometimes have profound effects (cf. questions about
whether abbreviations used by the tz distribution propoaged elsewhere,
or reflect common usage, etc., etc.). We should choose words with
care, and be silent the rest of the time.

> +# with it, use "posix_only" or "posix_right".  POSIX time is often combined
> +# with leap smearing,

Leap smearing is still an experimental activity, and its consequences are not
well-understood. I do not think we can fairly say "often" used, or
"often" combined with POSIX time.

> as this is more accurate than strict POSIX time

I don't see how the accuracy or precision improves with leap smearing.
Some could say it degrades.

> +# and it often works better than "right" time with applications that
> +# are not leap second aware.

Again, I don't think there is support for claims of "often."

> +    tz-link.htm now covers leap smearing, which is popular in clouds.

I don't know that leap smearing is "popular." It is used by Amazon and
Google for sure. I'm certainly not comfortable saying it is popular when
we don't have to say anything.

The biggest problem we have with leap smearing is that smeared time
is not clearly traceable. If it were in its own zone and we could see

  Sat Dec 31 23:59:59.999 UTC 2016


  Sat Dec 31 23:59:59.499 UTC-SMEARED24h 2016

then the world would be improved. I don't know that the tz package
can usefully get us there.

But if not, I think the less said in the tz distribution about leap
smearing, the better.

I am similarly uncomfortable with the text added to tz-link.htm,
but if there isn't broad agreement that we should be a lot more careful
in our language, it's not helpful to critique that.

--jhawk at mit.edu
  John Hawkinson

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