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

Paul Eggert eggert at cs.ucla.edu
Mon Dec 5 07:33:05 UTC 2016

John Hawkinson wrote:

> I do not think we can fairly say "often" used, or
> "often" combined with POSIX time.

Although it's pretty common, we indeed don't have to say "often".

>> as this is more accurate than strict POSIX time
> I don't see how the accuracy or precision

With leap smearing, the ideal clock is at most 0.5 s off UTC, as opposed to 
being at most 1.0 s off with strict POSIX time.

> we don't have to say anything.

Given the popularity of leap smearing, and the fact that this Makefile section 
advises users whether to use "posix" or "right" time, the section should say 
something -- otherwise people are more likely to incorrectly choose "right" time 
on a system that uses leap smearing.

> The biggest problem we have with leap smearing is that smeared time
> is not clearly traceable.

Yes, that would be a nice problem to fix somehow. Perhaps append "-A" to the 
time zone indication when the clock is using AWS-style leap smearing? And we 
could append "-P" for strict POSIX time (hmm, but that's the default, so perhaps 
not....). Just thinking out loud. Anyway, it's not a problem we can easily fix 
just by changing Makefile comments.

Proposed Makefile patch attached.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0001-Makefile-Tone-down-leap-smearing-discussion.patch
Type: text/x-diff
Size: 1513 bytes
Desc: not available
URL: <http://mm.icann.org/pipermail/tz/attachments/20161204/6a5fb903/0001-Makefile-Tone-down-leap-smearing-discussion-0001.patch>

More information about the tz mailing list