[LEAPSECS] operational time -- What's in a name?

[Steve Allen]

On Thu 2008-02-14T22:16:59 +0000, Poul-Henning Kamp hath writ:

> In message <20080214221022.GA20007 at ucolick.org>, Steve Allen writes:

> >That's what they said about changing the conventional longitudes of

> >every observatory on the planet in order to get agreement on the value

> >of UT starting in 1962.  But in 1961 the IAU said "do it", and they

> >did -- even in cases where it caused a time step in the sovereign time

> >scale of a nation, and even where it introduced a new, potentially

> >ambiguous notion of origin of longitude for civil mapping.

>

> This comparison is so bogus that we ought to frame and hang it.

>

> In 1961, the task was on a few handfulls of scientific people, most,

> if not all, of them phd's, and all of them very much at home in the

> subject domain.

>

> Fiddling with time_t today would involves more than a million

> persons, very few of which can readily tell you what a leap-second is.


I disagree.  All of the technical part falls into the hands of the
folks who maintain the zoneinfo files and their code equivalents
(including other, non-POSIX systems for timezone offsets).  The actual
number of people who have to know what they are doing is probably
comensurable with the number of people in the time bureaus in 1962.

The rest of those million people need merely install a zoneinfo and
code update as they do every time any jurisdiction decides to change
the dates of its daylight time transition.

So again, the notion is this:

That the ITU-R follow the recommendations that were produced at their
own colloquium in Torino (instead of letting their spokespersons
misrepresent that meeting saying that it did not call for a new name.
There are precedents for choosing a new name, look here
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1978QJRAS..19..290S
to see a description of the confusion caused by the Royal Navy's
Admiralty.)

That the ITU-R adopt a leap free broadcast timescale with the new name
something like International Time (TI) to be defined much more simply
than the current UTC as TAI minus however many leap seconds have
effectively been inserted since 1958-01-01.

That the ITU-R relinquish UTC to BIPM and IERS, allowing them to deal
with the civil time issues of leap seconds while the ITU-R focusses
solely on the technical issues of systems that need uniform time.

That POSIX time_t henceforth be interpreted as TI, and that the leap
seconds go into the zoneinfo files such that most time zones,
including UTC, start being a number of hours minus leap seconds off
from TI.

And the consequence of any of those million people not doing the
update is minimal.  After the first leap second their clock is off by
only 1 second, and their clock is still tracking an international
standard, now TI instead of UTC.

This is merely a name change from one standard to another.
It's akin to what happened in the US on 1966-12-01T00:00 when WWV
moved from Maryland to Colorado and changed from broadcasting Eastern
Standard Time to Mountain Standard Time.
It's akin to what happened in the US on 1967-04-28T21:00 when the
announcments from WWV and WWVH changed from saying Mountain Standard
Time and Hawaii Standard Time to GMT.
It's akin to what happened in the US on 1974-01-01 when WWV and WWVH
changed from announcing GMT to UTC -- yes, that's right, UTC didn't
really start in the US until two years after leap seconds.

The trick with the change of time worldwide in 1962 and 1972, and in
the US in 1966, 1967, and 1974, was to preserve the characteristics of
the *operational* systems.  These changes in conventional longitudes,
and in name of the time scale, did not have any effect on operational
systems.

Even if those million people wait until the end of the century the
difference between the TI-based time and UTC-based time is only a
minute or so.  And here I note that the same argument raised by the
folks who want to abandon leaps in UTC applies the other direction,
too:

If it is of little consequence for most clocks to be off from the sun
by a minute or so, then it is of little consequence for most clocks to
be using one international time standard or another that differ by a a
few seconds.  I can't predict traffic congestion well enough to arrive
at work within a given minute, let alone a second, and that's most of
the purpose of civil time.

The operational systems won't care about the name of the system
they're using, and most every other system where the difference of
consequence will get upgraded to use a new scheme before the
difference is more than a few seconds.

We have the ability to do this either way.  What we have to decide is
whether we will abandon the notion that clock and calendar are related.

--
Steve Allen                 <sla at ucolick.org>                WGS-84 (GPS)
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