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

Paul Eggert eggert at cs.ucla.edu
Mon Dec 5 07:59:24 UTC 2016

John Hawkinson wrote:

> your patch only changes the Makefile, not the tz-link.htm file

I changed tz-link.htm in the previous email.

> I think we would say that with a leap smearing, the clock is
> KNOWN to be inaccurate, by up to 0.5 seconds, and a POSIX UTC clock is
> exactly correct, except maybe during the one second of the positive
> leap.

There's no "maybe" about it. The POSIX clock stops cold during a leap second, 
and is therefore 1 s off just before the leap second finishes. I.e., the POSIX 
clock is also known to be inaccurate.

> If people are choosing "right" on the basis of what's in there,
> something is probably terribly wrong

That part of the Makefile was not-so-subtly advocating "right" time. That 
advocacy made sense when "right" time was the only automatic way to deal with 
leap seconds. Nowadays other approaches are more popular in practice, so it 
makes sense to tone down the advocacy and to say how "posix" and "right" 
interoperate with these other approaches, which is what the recently-proposed 
changes are trying to do.

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