Re: ITU Meeting last year

2005-01-20 Thread Markus Kuhn
[EMAIL PROTECTED] wrote on 2005-01-19 20:19 UTC:
 A resolution was proposed to redefine UTC by replacing leap seconds by leap
 hours, effective at a specific date which I believe was something like 2020.

Thanks for the update!

Did the proposed resolution contain any detailed political provisions
that specify, who exactly would be in charge of declaring in about six
centuries time, when exactly the first UTC leap hour should take place?

Will IERS send out, twice a year, bulletins for the next *600 years*,
announcing just that UTC will continue as usual for the next 6 months?
Not the most interesting mailing list to be on ...

And when the day comes, will people still recognize the authority of
IERS and ITU in such matters? Keep in mind that the names, identities,
and structures of these instritutions will likely have changed several
times by then. Also keep in mind that any living memory of the last UTC
leap will then have been lost over twenty generations earlier. The
subject won't get any less obscure by making the event a 3600x more rare
occasion.

If this proposal gets accepted, then someone will have to shoulder the
burden and take responsibility for a gigantic disruption in the
global^Wsolar IT infrastructure sometimes around 2600. I believe, the
worry about Y2K was nothing in comparison to the troubles caused by a
UTC leap hour. We certainly couldn't insert a leap hour into UTC today.

In my eyes, a UTC leap hour is an unrealistic phantasy.

Judging from how long it took to settle the last adjusting disruption of
that scope (the skipping of 10 leap days as part of the Gregorian
calendar reform), I would expect the UTC leap hour to become either very
messy, or to never happen at all. Who will be the equivalent of Pope
Gregory XIII at about 2600 and where would this person get the authority
from to break thoroughly what was meant to be an interrupt-free computer
time scale. Even the, at the time, almightly Catholic Church wasn't able
to implement the Gregorian transition smoothly by simply decreeing it.

Do we rely on some dictator vastly more powerful than a 16-th century
pope to be around near the years 2600, 3100, 3500, 3800, 4100, 4300,
etc. to get the then necessary UTC leap hour implemented?

Remember that UTC is used today widely in computers first of all because
it *lacks* the very troublesome DST leap hours of civilian time zones.
Most of the existing and proposed workarounds for leap seconds (e.g.,
smoothing out the phase jump by a small temporary frequency shift) are
entirely impractical for leap hours.

Please shoot down this leap-hour idea. The problem is not solved by
replacing frequent tiny disruptions with rare catastrophic ones. It is
hardly ethical to first accept that a regular correction is necessary,
but then to sweep it under the carpet for centuries, expecting the
resulting mess to be sorted out by our descendents two dozen generations
later on.

Leap hours are 3600 more disruptive than leap seconds!

If ITU wants to turn UTC into an interrupt-free physical time scale
decoupled from the rotation of the Earth, then it should say so
honestly, by defining that UTC will *never* ever leap in any way,
neither by a second, nor by an hour.

Markus

--
Markus Kuhn, Computer Lab, Univ of Cambridge, GB
http://www.cl.cam.ac.uk/~mgk25/ | __oo_O..O_oo__


Re: ITU Meeting last year

2005-01-20 Thread Clive D.W. Feather
Markus Kuhn said:
 A resolution was proposed to redefine UTC by replacing leap seconds by leap
 hours, effective at a specific date which I believe was something like 2020.

[...]
 If this proposal gets accepted, then someone will have to shoulder the
 burden and take responsibility for a gigantic disruption in the
 global^Wsolar IT infrastructure sometimes around 2600. I believe, the
 worry about Y2K was nothing in comparison to the troubles caused by a
 UTC leap hour. We certainly couldn't insert a leap hour into UTC today.

 In my eyes, a UTC leap hour is an unrealistic phantasy.
[...]

I may be wrong here, but I thought the leap hour idea did *not* insert a
discontinuity into UTC. Rather, in 2600 (or whenever it is), all civil
administrations would move their local-UTC offset forward by one hour,
in many cases by failing to implement the summer-to-winter step back.

Thus in the UK and the US eastern seaboard, the civil time would go:

  UK   US east
Summer 2599:   UTC + 0100UTC - 0400
Winter 2599/2600:  UTC + UTC - 0500
Summer 2600:   UTC + 0100UTC - 0400
Winter 2600/2601:  UTC + 0100UTC - 0400
Summer 2601:   UTC + 0200UTC - 0300
Winter 2601/2602:  UTC + 0200UTC - 0400

That *is* practical to implement, though coordination might be harder. On
the other hand, adminstrative areas that are near the edge of a zone now
could move earlier if they wanted. The world is used to time zones, after
all.

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Re: ITU Meeting last year

2005-01-20 Thread John Cowan
Markus Kuhn scripsit:

 In my eyes, a UTC leap hour is an unrealistic phantasy.

I agree.  But the same effects can be achieved by waiting for local
jurisdictions to change the existing LCT offsets as the problem becomes
locally serious.  They've done it many times in the past and can easily
do so again.  The fact that America/New_York is either five or four hours
behind UTC is not carved in stone anywhere, it's just what happens to
work right now.  A change to being either four or three hours behind
will not have nearly the same disruptive effect as a disruption in UTC.

And perhaps people won't even bother.  If people in Urumqi right now
can tolerate a three-hour difference between LMT and LCT, a slightly
different relation between the sun and the clock may seem quite tolerable
to our great^20-grandchildren.

(Astronomers will howl.  They doubtless howled when we broke the
connection between the calendar and the synodic month, too.  IERS can
even maintain OldUTC for their benefit; what matters is what the basis of
LCT is, since we all live our lives primarily by LCT.)

--
In politics, obedience and support  John Cowan [EMAIL PROTECTED]
are the same thing.  --Hannah Arendthttp://www.ccil.org/~cowan


Re: ITU Meeting last year

2005-01-20 Thread John Cowan
Clive D.W. Feather scripsit:

 That *is* practical to implement, though coordination might be harder. On
 the other hand, adminstrative areas that are near the edge of a zone now
 could move earlier if they wanted. The world is used to time zones, after
 all.

For that matter, Newfoundland could decide to change its offset from the
current -0330 to -0300 in 2300, and then leave it alone until 2900.
The world would spin on quite unaffected.  (Newfie joke suppressed here.)

--
John Cowan  [EMAIL PROTECTED]
http://www.reutershealth.comhttp://www.ccil.org/~cowan
Humpty Dump Dublin squeaks through his norse
Humpty Dump Dublin hath a horrible vorse
But for all his kinks English / And his irismanx brogues
Humpty Dump Dublin's grandada of all rogues.  --Cousin James


Re: ITU Meeting last year

2005-01-20 Thread Markus Kuhn
Clive D.W. Feather wrote on 2005-01-20 12:34 UTC:
  A resolution was proposed to redefine UTC by replacing leap seconds by leap
  hours, effective at a specific date which I believe was something like 
  2020.

 I may be wrong here, but I thought the leap hour idea did *not* insert a
 discontinuity into UTC.

I think, the phrase to redefine UTC by replacing leap seconds by leap
hours can only mean going from

  |UTC - UT1|  1 s

to something like

  |UTC - UT1|  1 h

(or some other finite |UTC - UT1| bound like that).

That was certainly the idea of the BIPM proposal presented at the Torino
meeting.

 Rather, in 2600 (or whenever it is), all civil
 administrations would move their local-UTC offset forward by one hour,
 in many cases by failing to implement the summer-to-winter step back.

Such a proposal would be called to redefine UTC by eliminating future
leaps (i.e., by establishing a fixed offset between UTC and TAI). It
seems perfectly practical, at least as long as |UTC - UT1|  24 h
(i.e., for the next 5000 years).

What local governments with regional civilian time zones do is outside
the influence of the ITU. But if leap seconds were eliminated from UTC
and a fixed TAI-UTC offset defined instead, then what you describe above
is indeed what I would expect to happen with most of them. Unless we
give up the notion of local time zones entirely, there would be a clear
need to keep them locked to UT1 + offset to within an hour or so.

Markus

--
Markus Kuhn, Computer Lab, Univ of Cambridge, GB
http://www.cl.cam.ac.uk/~mgk25/ | __oo_O..O_oo__


Re: ITU Meeting last year

2005-01-20 Thread Steve Allen
On Thu 2005-01-20T13:39:58 +, Markus Kuhn hath writ:
 That was certainly the idea of the BIPM proposal presented at the Torino
 meeting.

As seen on my online bibliography web page, the proposal probably was
a slightly evolved form of this document

http://www.fcc.gov/ib/sand/irb/weritacrnc/archives/nc1893wp7a/1.doc

--
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Re: ITU Meeting last year

2005-01-20 Thread Poul-Henning Kamp
In message [EMAIL PROTECTED], John Cowan writes:
Markus Kuhn scripsit:

 In my eyes, a UTC leap hour is an unrealistic phantasy.

I think your critizism of it is just as unrealistic.

If 600 years down the road we have colonized the solar system, then a
large fraction of the population wouldn't care about terrestial
solar time anyway, and I'm sure the leap hour will be cancled well
in advance.

Given that the average western citizen under 30 years already today
can barely add up three items in the supermarket without resorting
to their mobile phones built in calculator today, I think you can
safely assume that you can do anything to the timescale 100 years
from now.

At that time most people will just as they're told on television
(probably in 3D and with full olfactory support) and the few
scientists who care will be bogged down in a very theoretical
discussion about what it would have done to the cows milk, had cows
not been outlawed for foodstuff production many years ago.

Considering that the last couple of changes to our timescales were
forced through in very short time, say 20 years to be very generous
then we can change our timescales 130 times between now and the
first leap-hour, and that is provided earthquakes and yet unknown
geophysics don't make them unnecessary or make it more necessary.

We certainly don't need to decide now who is going to call the leap
hour 600 years from now, all we need to decided is who gets to call
it as long as the next treaty on time is in force.  If that turns
out to be 600 years, then it stands for 600 years, if ten years
from now we find out what the real nature of time is and need to
make a new timescale, then somebody had an easy job for 10 years.

The one thing we don't need is flaming rethoric...

--
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
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Re: ITU Meeting last year

2005-01-20 Thread Poul-Henning Kamp
In message [EMAIL PROTECTED], Tom Van Baak writes:

If one uses the rough but often-quoted figure of
one leap second about every 500 days then
a leap hour would be required on the order of
500 * 3600 / 365 = ~5000 years from now.

It's not a linear curve, it's quadratic.  I found some
slides from the torino meeting where this was laid out very
well but I didn't save the URL, sorry.

--
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
[EMAIL PROTECTED] | TCP/IP since RFC 956
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Re: ITU Meeting last year

2005-01-20 Thread Steve Allen
On Thu 2005-01-20T09:33:01 -0800, Tom Van Baak hath writ:
 So it's safe to say we're talking millennia rather
 than centuries, yes? I wonder where the notion
 that it's just a few centuries away came from.

If there is something not clear in the presentation on

http://www.ucolick.org/~sla/leapsecs/dutc.html

I would be obliged to know about it.


--
Steve Allen  UCO/Lick Observatory   Santa Cruz, CA 95064
[EMAIL PROTECTED]  Voice: +1 831 459 3046 http://www.ucolick.org/~sla
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Re: ITU Meeting last year

2005-01-20 Thread Tom Van Baak
 It's not a linear curve, it's quadratic.  I found some
 slides from the torino meeting where this was laid out very
 well but I didn't save the URL, sorry.

Ah, yes, I forgot the quadratic term. Steve Allen has
a nice page at:

http://www.ucolick.org/~sla/leapsecs/dutc.html

And his table shows the first leap hour would occur
in the year 2500 to 2600 time frame. So that's where
the 500 or 600 year value people quote comes from;
it's a few centuries from now, not millennia afterall.

Thanks,
/tvb
http://www.LeapSecond.com


Re: ITU Meeting last year

2005-01-20 Thread Poul-Henning Kamp
In message [EMAIL PROTECTED], Steve Allen writes:
On Thu 2005-01-20T09:33:01 -0800, Tom Van Baak hath writ:
 So it's safe to say we're talking millennia rather
 than centuries, yes? I wonder where the notion
 that it's just a few centuries away came from.

If there is something not clear in the presentation on

http://www.ucolick.org/~sla/leapsecs/dutc.html

I enjoyed your page a lot some time ago when I fell over it.

Thanks a lot for the effort.

--
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
[EMAIL PROTECTED] | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.


Re: ITU Meeting last year

2005-01-20 Thread Steve Allen
On Thu 2005-01-20T12:34:09 +, Clive D.W. Feather hath writ:
 I may be wrong here, but I thought the leap hour idea did *not* insert a
 discontinuity into UTC. Rather, in 2600 (or whenever it is), all civil
 administrations would move their local-UTC offset forward by one hour,
 in many cases by failing to implement the summer-to-winter step back.

The text of the document from USWP 7A continues the trend that has
been displayed publicly for several years now, namely that UTC would
officially switch from leap seconds to leap hours.  This is clearly an
artifice, for there can be no expectation that people 5 centuries
hence will respect the content of any revision of ITU-R TF.460 made
today.  It is not even clear that the BIPM is ready to respect it now.

Looking at the players, however, a plausible reason for the artifice
becomes clear.  Many of the proposers are employees of agencies of the
US Federal government.  Under federal law the legal time of the United
States is specified as mean astronomical time, and in the parlance
of the era of that legislation that clearly must be interpreted as the
form of earth rotation time known as mean solar time.  The most recent
attempt to change the wording of the US Code failed.

To propose the complete abolition of leaps would be to propose a time
scale which demonstrably violates federal law.  To propose leap hours
is to propose an artifice which keeps the proposers from using their
positions to advocate a violation of federal law.  Legal fiction is
a well-tested means of effecting change.

It is hard to say what the actual intent is when so few documents have
made it out of the inner sanctum of the Time Lords.

In the hopes of enlightenment for this list, but without the ability
to authenticate these draft documents, I offer the following:

http://www.ucolick.org/~sla/leapsecs/SRG7Afinalreport.doc
http://www.ucolick.org/~sla/leapsecs/PropRevITU-RTF460-6.doc

It seems that atomic clock keepers have lost all interest in the
continued existence of mean solar time, sundials, or the analemma.

--
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Re: ITU Meeting last year

2005-01-20 Thread Poul-Henning Kamp
In message [EMAIL PROTECTED], Steve Allen writes:

In the hopes of enlightenment for this list, but without the ability
to authenticate these draft documents, I offer the following:

http://www.ucolick.org/~sla/leapsecs/SRG7Afinalreport.doc
http://www.ucolick.org/~sla/leapsecs/PropRevITU-RTF460-6.doc

Looks good to me.

It seems that atomic clock keepers have lost all interest in the
continued existence of mean solar time, sundials, or the analemma.

And why shouldn't they ?  The job of atomic clock keepers is to
keep TAI ticking.

I really can't see any problem with the proposal above which even
get into the same order of magnitude to the problems and inconvenience
leapseconds are today.  And I applaud them for setting a transition
date which I think would spare us for even one more leap-second.

As a private person living at 11°20'22.98 the sun is never in south
at noon anyway and we have voluntarily moved it a further 15° away
from south half the year already with daylights savings time.  I
already need to adjust my sundial twice a year anyway (OK, so I'm
also at 55°N24' so it's not much use during winter so I don't
actually bother but that's besides the point :-).

As a computer nerd I can fully appreciate the problems and cost of
converting existing systems to cope with larger UT1/UTC difference,
but that cost would be peanuts compared to the costs of implementing
leap-seconds reliably in future systems that would need it.

And for that conversion cost:  Just how hard is it to make a computer
synchronize with NTP over the internet, pick the DUT1 up from IERS
homepage and emit clocksignals which are UT1 approximations for those
old computers anyway ?

I know several operations computers here in Denmark which think it
is 1985 because they cannot cope properly with years in a different
century, people can live with that kind of quirk in old computers.

Finally as goes with navigation, here in Denmark celestial navigation
is now taught as a historical interest course...

So yes, we might loose a ship or two if they for some reason rely on
celestial navigation.  Chances are very good that they were in dire
straits already, otherwise they wouldn't have taken their eye off
the GPS receiver and the radar long enough to locate the sekstant.

Compare that to the number of deaths of just one major software bug
triggered by a leapsecond, and things come into perspective nicely.

--
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
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Re: ITU Meeting last year

2005-01-20 Thread John Cowan
Steve Allen scripsit:

 If there is something not clear in the presentation on

 http://www.ucolick.org/~sla/leapsecs/dutc.html

 I would be obliged to know about it.

It's very clear and useful.  But:


 At Torino the proponents of omitting leap seconds supposed that the
 governments of the world might handle this situation using leap hours
 introduced into civil time by occasionally omitting the annual ``spring
 forward'' change to jump to summer/daylight time. However there are
 serious questions raised by the notion of a leap hour. Given that the
 first leap hour would not happen for centuries, it is not clear that any
 systems (legal or technological) would build in the necessary complexity
 for handling it.

Systems already have existing mechanisms for handling large secular changes in
LCT.  There are many places that adjust their daylight time mechanisms on
a yearly basis anyhow.

--
Where the wombat has walked,John Cowan [EMAIL PROTECTED]
it will inevitably walk again.  http://www.ccil.org/~cowan