Re: [Ntp] New Version Notification for draft-gruessing-ntp-ntpv5-requirements-03.txt

[Steve Allen <[e-mail]>]

On Thu 2021-10-21T15:37:45+0200 [e-mail] hath writ:
> The whole issue is a bit politically/socially (?) charged, where some
> people have a fundamental resistance of de-coupling coordinated time from
> experienced (solar) time.

At the 2015 ITU-R WRC the original draft document had three options
for change of the way that UTC is defined.  When that draft was
circulated six nations objected and the final document of options
included a 4th option which was, paraphrased "You all have spent 15
years trying to redefine UTC and in all of that time none of the
documents provided for consideration have explained why leap seconds
exist nor the consequences for abandoning them; therefore do nothing."
The result of the 2015 WRC was nothing.

One problem is that most people, and the laws in most nations, expect
that a legal calendar day is determined by observing the rotation of
the earth.  In particular, the laws in many nations explicitly state
that legal time is mean solar days and/or GMT.  A purely atomic time
scale with no leap seconds is not mean solar time.  A "UTC" without
leap seconds would therefore not be legal in many places, and thus not
suitable for an international recommendation.

> kinda hope the solution is to increase the maximum difference to an hour,

The "leap hour" was proposed early in 21st century discussions by the
delgation from the USA.  It was ridiculed as even harder to enforce
and implement than the leap second, but at the time of that proposal
the legal time of the USA was explicitly based on GMT, therefore the
delegation from the USA could not legally submit a proposal that
called for UTC to deviate indefinitely from mean solar time.

The leap second exists in the first place because the old form of
atomically coordinated time which was the international agreement in
the 1960s had radio broadcasts of atomically-regulated seconds with a
duration longer than the SI second which was adopted in 1967.  Every
national metrology agency which adopted that old scheme was able to
broadcast time signals that agreed to within a millisecond.  Not every
nation adopted the old form of coordinated time; in particular the
Soviets never used it.

After the adoption of the SI second Germany passed a law which defined
all legal metrology in Germany to be based on SI units, and it changed
the national metrology agencies which were responsible for certifying
those measurements.  Responsibility for time in Germany was removed
from the longstanding hydrology institute which observed the sky and
given solely to PTB.  PTB decided that it would be illegal to
broadcast any kind of second other than the SI second, therefore in
less than two years Germany would no longer conform with the existing
international agreement for broadcast time signals.  That started a
scramble to forge a new international agreement which would be
acceptable everywhere.

Many meetings were ex parte, proceedings were not recorded (or even
redacted -- there is one international meeting which was annulled,
removed from offical history, and re-held a year later).  The final
tweaks to the agreement that was implemented were based on meeting
with a Soviet representative in order to get USSR to join, even though
those tweaks made it impossible to implement the agreement as it had
been approved by the CCIR.

It is clear they agreed that any new agreement must be legal in all
countries, therefore it must provide mean solar time.  Thus came the
leap second as a means of reaching a new acceptable consensus quickly,
without having to wait for most of the nations of the world to
redefine legal time, and without the risk that some nations might
legislate otherwise.

Among the documents that did survive was an IAU report which said that
leap seconds would be disastrous.  Its authors recognized that they
were being ignored in the haste to reach a new international
agreement, but also their position did not enable them to poison such
an agreement.  What they could and did do was to announce that the
operational radio navigation systems they controlled would be purely
atomic time without leap seconds, and that astronomical times would
continue to use Universal Time.  That need for two different time
scales was something that astronomers had recognized for decades
before the leap second, but which national laws still cannot grok.

--
Steve Allen                    <[e-mail]>              WGS-84 (GPS)
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