| Re: [chrony-dev] "leapsectz" and leapsecond announce (was:refclock: Add a new "tai" option) |
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William G. Unruh __| Canadian Institute for|____ Tel: +1(604)822-3273
Physics&Astronomy _|___ Advanced Research _|____ Fax: +1(604)822-5324
UBC, Vancouver,BC _|_ Program in Cosmology |____ unruh@xxxxxxxxxxxxxx
Canada V6T 1Z1 ____|____ and Gravity ______|_ www.theory.physics.ubc.ca/
On Thu, 12 Oct 2017, FUSTE Emmanuel wrote:
It is also possible that a leap second is subtracted rather than added, and
the code should take that into account. (But by now, it is doubtful that any
negative leap seconds will occur in the future, unless perhaps there are a
bunch of really powerful earthquakes which change the moment of intertia of
the earth.
Which is possible crazy people with nuclear power in hand...
Although I agree with the sentiments, that would not make a sufficient impact
on the moment of inertial of the earth to change the rate of spin.
One side question about "leapsectz" option: Does the use of the option
imply ignoring leap announcements from other ntp servers or sources ?
Which would imply that the timezone database MUST be maintained up to
date to honor any future leap ?
Yes.
Or leap announcement is taken into account but utc-tai offset lost in
case of a restart ?
Unless you have an up-to-date database. Unfortunately unless you have a
TAI-UTC database (ie a leapsecond database) the system has no way of knowing
what the relation is between the two. Some GPS will deliver not only UTC but
also the offset between UTC and GPS time. GPS time is a fixed offset from TAI,
[19 sec behind according to http://www.leapsecond.com/java/gpsclock.htm]
In any case, a little add to clarify this point would be great in the
"leapsectz" option documentation.
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