Re: how to reset a clock

2007-01-04 Thread John Cowan
Rob Seaman scripsit:

 And, of course, a ship would not carry a single clock, but two or
 more.  Friendly ships meeting at sea would also exchange clock
 readings - creating the first ensemble time scale.  (Some things
 never change.)

English passenger at Irish railway station, pointing to the two clocks
at either end:  Why don't those clocks tell the same time?

Irish stationmaster:  Ahhh, what would we be wanting with *two* clocks
if they told the same time?

Eoghan Mac Eoghain

--
It was dreary and wearisome.  Cold clammy winter still held way in this
forsaken country.  The only green was the scum of livid weed on the dark
greasy surfaces of the sullen waters.  Dead grasses and rotting reeds loomed
up in the mists like ragged shadows of long-forgotten summers.
--The Passage of the Marshes  http://www.ccil.org/~cowan


Re: A lurker surfaces

2007-01-02 Thread John Cowan
Zefram scripsit:

 Projecting into the future, one can foresee the eventual abandonment of
 timezones in favour of the universal use of Universal Time.

I think that's over the top.  Bureaucratically it is just too annoying
if the large majority of people have a work shift that overlaps legal
midnight.

--
On the Semantic Web, it's too hard to prove John Cowan[EMAIL PROTECTED]
you're not a dog.  --Bill de hOra   http://www.ccil.org/~cowan


Re: Introduction of long term scheduling

2007-01-02 Thread John Cowan
Warner Losh scripsit:

 There's an exception for IERS to
 step in two weeks in advance if the earth's rotation rate hickups.

So if I understand this correctly, there could be as many as 14
consecutive days during which |DUT1|  0.9s before the emergency leap
second can be implemented; consequently, the current guarantee is only
statistical, not absolute.

--
John Cowan  http://www.ccil.org/~cowan  [EMAIL PROTECTED]
After all, would you consider a man without honor wealthy, even if his
Dinar laid end to end would reach from here to the Temple of Toplat?
No, I wouldn't, the beggar replied.  Why is that? the Master asked.
A Dinar doesn't go very far these days, Master.--Kehlog Albran
Besides, the Temple of Toplat is across the street.  The Profit


Re: Introduction of long term scheduling

2007-01-02 Thread John Cowan
Warner Losh scripsit:

 There's no provision for emergency leapseconds.  They just have to be
 at the end of the month, and annoucned 8 weeks in advance.  IERS has
 actually exceeded this mandate by announcing them ~24 weeks in advance
 in recent history.

So much the worse.  That means that if the Earth hiccups on March 7, the
value of |DUT1| will not return to normal until May 31.

--
John Cowan[EMAIL PROTECTED]http://ccil.org/~cowan
The whole of Gaul is quartered into three halves.
-- Julius Caesar


Re: A lurker surfaces

2007-01-01 Thread John Cowan
Michael Sokolov scripsit:

 The people who complain about leap seconds screwing up their interval
 time computations are usually told to use TAI.  They retort that they
 need interval time *between civil timestamps*.  To me that seems like
 what they are really measuring as interval time is not physical
 interval time, but how much time has elapsed *in civil society*.

I think this point is quite sound, but I don't quite see what
its implications are (or why it makes rubber seconds better than
other kinds of adjustments).

--
John Cowan   http://ccil.org/~cowan[EMAIL PROTECTED]
We want more school houses and less jails; more books and less arsenals;
more learning and less vice; more constant work and less crime; more
leisure and less greed; more justice and less revenge; in fact, more of
the opportunities to cultivate our better natures.  --Samuel Gompers


Re: A lurker surfaces

2007-01-01 Thread John Cowan
Ashley Yakeley scripsit:

 Rubber seconds are appropriate because we have rubber days. People
 who need absolute time have their own timescale based on some
 absolute unit (the SI second), but to everyone else, the second is
 a fraction of the day.

Well, okay.  Does the rubberiness go down all the way?  Is a civil
nanosecond one-billionth of a civil second, then?  If so, how do we
build clocks that measure these intervals?


--
One art / There is  John Cowan [EMAIL PROTECTED]
No less / No more   http://www.ccil.org/~cowan
All things / To do
With sparks / Galore -- Douglas Hofstadter


Re: Mechanism to provide tai-utc.dat locally

2006-12-29 Thread John Cowan
Rob Seaman scripsit:

 Seems like?  Chances are?  Pick some other random technical issue -
 say, automobile airbags, standardized educational testing, the lead
 content of pigment in children's crayons, and so forth and so on.
 Would seems like and chances are be phrases you would want to see
 in a white paper discussing the costs, benefits and risks of these?

Diffidently I suggest that if you think cost/benefit analysis has
*anything* to do with how international standards are set, you are
fairly unfamiliar with the actual process.

Those who enjoy law and sausage should not watch them being made.

--
I don't know half of you half as well   John Cowan
as I should like, and I like less than half [EMAIL PROTECTED]
of you half as well as you deserve. http://www.ccil.org/~cowan
--Bilbo


Re: Mechanism to provide tai-utc.dat locally

2006-12-28 Thread John Cowan
Tony Finch scripsit:

 Still, your minute/month system does not deal with variable-length days.

I assume you mean 23-hour or 25-hour LCT days?  True.  It does work
against UCT days, though, since they are uniformly 1440 minutes long.

--
Overhead, without any fuss, the stars were going out.
--Arthur C. Clarke, The Nine Billion Names of God
John Cowan [EMAIL PROTECTED]


Re: Mechanism to provide tai-utc.dat locally

2006-12-28 Thread John Cowan
Rob Seaman scripsit:

 I don't care if you want to implement leap-milliseconds, as long
 as you tell me 10 years in advance when they happen.

 Again - with no intent to minimize the issues - what supports this
 assertion?  Is there any reason to believe that 10 years advance notice
 would encourage projects and vendors to do anything other than ignore
 the requirement entirely?  A statement that 10 years, or 600 years,
 notice is all that is needed to resolve all the problems, smooth over
 all the complications, is entirely too glib.

You are confusing the question of fixity (which is what notice is
about) with granularity.  It's true that probably no one would bother
to implement the ALHP.  However, if computer technologists were handed a
list of leap seconds from now until 2015, and told Implement these, it
wouldn't matter how many or how few leap seconds there were.  But since
you astronomers insist on a fixed maximum for |DUT1|, no such table
can exist.

The proposal is this:  look at the trends, take your best shot at
working out a leap-year schedule for 10 years in the future, and then
live with it.

--
Newbies always ask: John Cowan
  Elements or attributes?  http://www.ccil.org/~cowan
Which will serve me best?  [EMAIL PROTECTED]
  Those who know roar like lions;
  Wise hackers smile like tigers.   --a tanka, or extended haiku


Re: Mechanism to provide tai-utc.dat locally

2006-12-28 Thread John Cowan
Rob Seaman scripsit:

 Indeed.  Go for it.  I look forward to reading your report.  Who and
 what interests are adversely affected in each case?  How are these
 effects mitigated as a function of the limit on DUT1?  Also, contrast
 what benefits accrue.  One would think that the responsibility for
 quantifying the implications of a change to a standard would fall on
 the parties proposing said change.

It can't possibly be.  Nobody can know what a change is going to
cost except those who are going to have to pay for it (or not
pay for it).  And even their word cannot necessarily be trusted.

In this case there are really two questions:  how much it would
cost to loosen DUT1 but leave it bounded, and how much it would
cost if it were only statistically, not absolutely, bounded.

--
Don't be so humble.  You're not that great. John Cowan
--Golda Meir[EMAIL PROTECTED]


Re: Mechanism to provide tai-utc.dat locally

2006-12-27 Thread John Cowan
Zefram scripsit:

 In the general case: to determine or use an interval of N calendar FOOs,
 it is convenient to represent the time as a linear count of calendar
 FOOs plus details of the exact position within the current FOO.  FOO may
 be minute, hour, day, week, month, or year.  I think there should be
 record formats for all of these cases (the native UTC format is one
 of these with FOO = day), with conversion functions between them and
 also a linear count of seconds.

That's overkill.  If we confine ourselves to the Gregorian calendar,
a time interval can be safely represented as a triple of months,
minutes, and seconds.  All time units longer than a month contain
a fixed and integral number of months, and all time units larger
than a minute and smaller than a month contain a fixed and integral
number of minutes.  (If we don't care about leap seconds, shock
horror, we can just use months and seconds.)

--
The man that wanders far[EMAIL PROTECTED]
from the walking tree   http://www.ccil.org/~cowan
--first line of a non-existent poem by: John Cowan


Re: Mechanism to provide tai-utc.dat locally

2006-12-27 Thread John Cowan
Rob Seaman scripsit:

 Mucking with leap seconds is equivalent to redefining the
 concept of a day.

Very true.  And adopting the Egyptian-Roman calendar redefined
the concept of a month.  Somehow civilization survived.

--
John Cowan   [EMAIL PROTECTED]   http://ccil.org/~cowan
I must confess that I have very little notion of what [s. 4 of the British
Trade Marks Act, 1938] is intended to convey, and particularly the sentence
of 253 words, as I make them, which constitutes sub-section 1.  I doubt if
the entire statute book could be successfully searched for a sentence of
equal length which is of more fuliginous obscurity. --MacKinnon LJ, 1940


Re: The fine print

2006-11-29 Thread John Cowan
Rob Seaman scripsit:

 If NIST and USNO, official agencies of the United States government,
 declare time-of-day to be distinct from time interval, who are we to
 disagree?  As the New York State Supreme Court rules in the play:

I should point out that for historical reasons, in New York State the
name Supreme Court is applied to the ordinary trial court for civil
and major criminal cases; there are two levels of appellate courts
above it.

--
John Cowan[EMAIL PROTECTED]http://ccil.org/~cowan
   There was an old manSaid with a laugh, I
 From Peru, whose lim'ricks all  Cut them in half, the pay is
   Look'd like haiku.  He  Much better for two.
 --Emmet O'Brien


Re: ADASS poster on UTC

2006-10-28 Thread John Cowan
Steve Allen scripsit:

 For most civil purposes time is only relevant to the nearest minute;

An obvious counterexample is taping TV shows: you don't want to miss
the first or last minute (modulo the presence of commercials).
I go to some trouble to keep my VCR synchronized with NTP time
to the nearest second or two.

--
There is no real going back.  Though I  John Cowan
may come to the Shire, it will not seem [EMAIL PROTECTED]
the same; for I shall not be the same.  http://www.ccil.org/~cowan
I am wounded with knife, sting, and tooth,
and a long burden.  Where shall I find rest?   --Frodo


Re: trading amplitude for scheduling

2006-08-04 Thread John Cowan
Tom Van Baak scripsit:

 In fact, leap seconds are simply due to the earth
 being slow. How it got to be slow and whether
 it is slowing are another issue.

Let me see if I have this right:

1) We have leap seconds because the Earth rotates more slowly
than once every 86,400 SI seconds.

2) Leap seconds will become more frequent in the future because
the Earth is decelerating.

3) Leap seconds occur irregularly because the Earth's deceleration
is not constant and in fact changes unpredictably.

Right?

--
LEAR: Dost thou call me fool, boy?  John Cowan
FOOL: All thy other titles  http://www.ccil.org/~cowan
 thou hast given away:  [EMAIL PROTECTED]
  That thou wast born with.


Re: trading amplitude for scheduling

2006-08-04 Thread John Cowan
Rob Seaman scripsit:

 Blame for what?  I'm left wondering.  Are we now fretting about
 the distinction between sidereal and solar time again?

I accidentally specified sidereal rather than mean solar days by
using the wording the Earth rotates.

 A leap hour is just 3600 embargoed leap seconds.

Indeed.  Which is why I am against the AHLP and in favor of letting
the SI seconds tick, allowing UT-TI to get as large as it likes, and
let the nations of the Earth make up the difference by adjusting their
local time offsets.  No, that won't last forever, but neither will any
other scheme -- when we get to the 36-current-hour day, the connection
with solar time will *have* to be broken, unless we have evolved (or
evolved ourselves) to cope with very different sleep-wake cycles.

BTW, are we now in a position to give a reasonable figure for the
mean and standard deviation of the Earth's deceleration, or do
we not have enough data yet?

--
Evolutionary psychology is the theory   John Cowan
that men are nothing but horn-dogs, http://www.ccil.org/~cowan
and that women only want them for their money.  [EMAIL PROTECTED]
--Susan McCarthy (adapted)


Re: trading amplitude for scheduling

2006-08-04 Thread John Cowan
Rob Seaman scripsit:

 Third result - even in the absence of lunar braking, leap jumps
 (or equivalent clock adjustments) would remain necessary.

Why is that?

If the SI second were properly tuned to the mean solar day, and the
secular slowing were eliminated, there would be no need to mess about with
the civil time scale, because the random accelerations and decelerations
would cancel out in the long run.  Of course, we'd have to tolerate larger
differences between clock time and terrestrial time, but we'd expect that.

--
We pledge allegiance to the penguin John Cowan
and to the intellectual property regime [EMAIL PROTECTED]
for which he stands, one world underhttp://www.ccil.org/~cowan
Linux, with free music and open source
software for all.   --Julian Dibbell on Brazil, edited


Re: independence day

2006-07-05 Thread John Cowan
Rob Seaman scripsit:

 The point is, however, that nothing - absolutely nothing -
 would then protect legal timekeeping in the U.S. or elsewhere from
 the whims of future timekeepers at the ITU.

I regret to state that this remark appears to me no more than
scaremongering.  The laws of the United States are not the
laws of the Medes and the Persians[*], subject to no repeal.
If the U.S. tied its legal time to the ITU, it could untie
it in future if that seems like a good idea.

In any case, changing the legal definition of U.S. time from GMT
to UTC merely regularizes the de facto position, since GMT no
longer has a specific international definition.

 What in practice would stop these individuals
 from leaping the clock forward or backward at will, or from changing
 the rate of UTC, or for that matter from making the clocks run
 backwards?

The fact of being rendered irrelevant, not to say a laughingstock.
What is to prevent the IERS from issuing bogus leap second announcements?

[*] I am not referring here to the Islamic Republic of Iran.

--
LEAR: Dost thou call me fool, boy?  John Cowan
FOOL: All thy other titles  http://www.ccil.org/~cowan
 thou hast given away:  [EMAIL PROTECTED]
  That thou wast born with.


Re: independence day

2006-07-05 Thread John Cowan
Rob Seaman scripsit:

 Why precisely, however, do you regret your inference?  If my
 arguments were to be deemed specious, surely that would strengthen
 opposing arguments (or at least remove competing options).

Because I'm not dueling with you, but trying to communicate my point of
view.  I regret, therefore, that I could not find better words
to do so.

(The fact that I was not dueling with [King] Argaven, but attempting
to communicate with him, was itself an incommunicable fact.  --Genly Ai
in Ursula K. Le Guin's _Left Hand of Darkness_)

 If the U.S. tied its legal time to the ITU, it could untie
 it in future if that seems like a good idea.

 and later in reply to Markus Kuhn:

 Reader, suppose you were an idiot, and suppose you were a member
 of Congress; but I repeat myself.   --Mark Twain (1882)

 You can't have it both ways.  Either a prudent decision making
 process is being followed, or it ain't.

These are not contradictory.  A good process *could* be followed; my
suspicion is that it won't be.  Despite Torino, I currently trust ITU in
such matters more than I trust the oligarchy in control of my own country.

 6) A time standard rooted in an ensemble of clocks, on the other
 hand, is subject to the vagaries of happenstance and history (like,
 say, another Napoleon).  What price to ensure 24/7/365/600
 reliability?  (I look forward to your riposte pointing out that the
 metric system emerged from the Reign of Terror :-)

Only in the sense that a revolution is a good time to change standards
of weights and measures (and money, as the U.S. did).

 What is to prevent the IERS from issuing bogus leap second
 announcements?

 Precisely the constraint that DUT1  0.9s.  Precisely the fact that
 UTC is currently tied to an underlying physical phenomena common to all.

A self-imposed constraint, I think.

--
That you can cover for the plentifulJohn Cowan
and often gaping errors, misconstruals, http://www.ccil.org/~cowan
and disinformation in your posts[EMAIL PROTECTED]
through sheer volume -- that is another
misconception.  --Mike to Peter


Re: building consensus

2006-06-08 Thread John Cowan
Rob Seaman scripsit:

 Of course, any old I, Claudius fan knows that Augustus was
 originally named Octavius.  Mere coincidence that the eighth child
 would end up naming the eighth month?

Almost certainly.  The eighth month was Sextilis, as July was originally
Quin(c)tilis.

--
John Cowan  [EMAIL PROTECTED]  http://ccil.org/~cowan
In computer science, we stand on each other's feet.
--Brian K. Reid


Re: building consensus

2006-06-08 Thread John Cowan
Clive D.W. Feather scripsit:

 I don't think John's referring to Against the Fall of Night versus
 The City and the Stars. Rather, at least in the latter, the official
 (cover) story of Diaspar (sp?) and the Invaders disagrees in many
 aspects with the true story as revealed by Vandemar (sp?).

Just so.  My best recollection now is that the moon was destroyed
either by the Empire or directly by Lys because it was approaching the
Earth too closely.  Presumably this reflects a state of affairs *after*
tidal locking, where the Moon's synchronous orbit begins to decay as a
consequence of the solar tides.

I read TCATS first, and recall it much better than ATFON.

--
John Cowan[EMAIL PROTECTED]http://ccil.org/~cowan
Heckler: Go on, Al, tell 'em all you know.  It won't take long.
Al Smith: I'll tell 'em all we *both* know.  It won't take any longer.


Re: building consensus

2006-06-08 Thread John Cowan
Poul-Henning Kamp scripsit:

 Old English had its own set of month names entirely unrelated to
 the Latin ones: if they had survived, they would have been Afteryule,
 Solmath 'mud-month', Rethe[math] 'rough-month', Astron [pl. of 'Easter'],
 Thrimilch 'three-milking', Forelithe, Afterlithe, Wedmath 'weed-month',
 Halimath 'holy-month', Winterfilth '-filling', Blotmath 'sacrifice-month',
 Foreyule.  At least some of these are obviously pre-Christian.

 They're practically all viking derived.

I think it more likely that the English and Norse forms have a
common proto-Germanic origin.

--
Dream projects long deferred John Cowan [EMAIL PROTECTED]
usually bite the wax tadpole.http://www.ccil.org/~cowan
--James Lileks


Re: building consensus

2006-06-07 Thread John Cowan
Poul-Henning Kamp scripsit:

 I belive this was because the year followed the taxation cycle of the
 government whereas the day+month followed the religiously inherited
 tradtion.

Indeed.  For that matter, the start of the U.K. tax year was left alone
when the calendar changed, and is now 6 April (it should be 7 April,
but for whatever reason no adjustment for 1900 was made).

--
We call nothing profound[EMAIL PROTECTED]
that is not wittily expressed.  John Cowan
--Northrop Frye (improved)


Re: building consensus

2006-06-07 Thread John Cowan
Rob Seaman scripsit:

 References for this?  Your explanation makes a lot of sense and I'm
 prepared to be convinced, but have been skeptical of experimental
 design as applied to questions of human behavior since participating
 in studies as a requirement of undergraduate psychology coursework.
 And if this cycle is inferred from the behavior of undergraduates,
 I'm even more skeptical :-)

I think there's some confusion here between the 24.7h period of the
diurnal mammal free-running clock and the 28h artificial cycles that
Nathaniel Kleitman and his student B.H. Richardson tried to put themselves
on over a 33-day period in Mammoth Cave back in 1938.  Richardson was
able to adapt to a 19h awake / 9h asleep cycle, but the much older
Kleitman was not.

The 24.7h result is quite consistent across diurnal mammals kept in
continuous darkness, including humans.   Google for circadian rhythms
for lots more detail.

--
John Cowan  [EMAIL PROTECTED]http://ccil.org/~cowan
No man is an island, entire of itself; every man is a piece of the
continent, a part of the main.  If a clod be washed away by the sea,
Europe is the less, as well as if a promontory were, as well as if a
manor of thy friends or of thine own were: any man's death diminishes me,
because I am involved in mankind, and therefore never send to know for
whom the bell tolls; it tolls for thee.  --John Donne


Re: building consensus

2006-06-05 Thread John Cowan
M. Warner Losh scripsit:

 : The designers of Posix time thought it was more important to preserve
 : the property that dividing the difference between two time_t values
 : by 60, 3600, 86400 would give minutes, hours, days.

 That's the one property that Posix time_t does not have.  The
 difference between time_t's that cross a leap second are off by one
 second, and therefore do not start with the right answer to do the
 division...

I expressed myself badly.  My point is that if you have a Posix time_t
representing 11:22:33 UTC on a certain day, and you add 86400 to that
time_t, you will get the Posix representation of 11:22:33 UTC on the
following day, whether a leap second intervenes or not.  This is a valuable
property, many existing programs depended on it, and the authors of the
Posix spec preserved it at the expense of having a distinct representation
for each UTC second.

You may call this position wrong (and I have done so), but it is
unquestionably defensible.

 It would be better to say the number of SI seconds since 1972 rather
 than UTC seconds, I think.

Indeed.

--
They do not preach  John Cowan
  that their God will rouse them[EMAIL PROTECTED]
A little before the nuts work loose.http://www.ccil.org/~cowan
They do not teach
  that His Pity allows them --Rudyard Kipling,
to drop their job when they damn-well choose.   The Sons of Martha


Re: building consensus

2006-06-05 Thread John Cowan
Rob Seaman scripsit:

 A schedule and a rule are the same thing, just regarded from
 different historical perspectives.  The leap day rule will most
 certainly have to accommodate scheduling changes over the millennia.

Fair enough, but there is a huge difference in practical terms between
a rule that will work for at least the next six centuries and a rule
that will only work for the next six months (i.e. no leap second before
2006-12-31T23:59:59Z).

 On the other hand, I am sure we haven't exhaustively discussed
 possible refinements to the leap second scheduling algorithm.  (And
 ain't that a rule?)

I thought the whole point was that while we had a rather good prediction
of changes in the tropical year (viz. none), and therefore only have to
dink with the calendar when the current error of about 8.46 seconds/year
accumulates to an uncomfortably large value, there is simply no knowing,
in the current state of our geophysical knowledge, how the wobbly old
boulder in the sky is going to wobble next.

 The biggest difference between leap days and leap seconds is that
 days are quantized.

Can you expound on this remark?

--
They tried to pierce your heart John Cowan
with a Morgul-knife that remains in the http://www.ccil.org/~cowan
wound.  If they had succeeded, you would
become a wraith under the domination of the Dark Lord. --Gandalf


Re: building consensus

2006-06-05 Thread John Cowan
Rob Seaman scripsit:

 So the calendar is either immutable - or it isn't :-)

The Gregorian calendar is immutable.  Whether it is in use at a certain
place is not.  Local time is on the Gregorian calendar today in the
U.S., but might conceivably be on the Revised Julian or even the Islamic
calendar a century hence.

 The Gregorian calendar succeeded the Julian, just as the Julian
 succeeded what came before.

But not everywhere at the same time, nor entirely.  There are still
versions of Orthodox Christianity that use the Julian calendar, the
decision being one for each autocephalous church within the Orthodox
communion.  To say nothing of Nova Scotia, which was first Gregorian,
then Julian, then Gregorian again.

Historians aren't exactly consistent on the question.  In European
history, dates are Julian or Gregorian depending on the location;
dates in East Asian history seem to be proleptic Gregorian.

(ObOddity:  It seems that in Israel, which is on UTC+3, the legal
day begins at 1800 local time the day before.  This simplifies
the accommodation of Israeli and traditional Jewish law.)

--
After fixing the Y2K bug in an application: John Cowan
WELCOME TO censored   [EMAIL PROTECTED]
DATE: MONDAK, JANUARK 1, 1900   http://www.ccil.org/~cowan


Re: building consensus

2006-06-05 Thread John Cowan
Rob Seaman scripsit:

 I wouldn't call this an oddity, but rather an interesting and
 elegant, one might even say charming, local custom.  The logic of
 this accommodation between 6:-00 pm clock time and a mean sunset
 demonstrates another weakness in the ALHP, since clock time would
 drift secularly against mean solar time.

Only if Israel never changes its time zone.

I found another spectacular illustration of how massive the difference
between solar and legal time can be.  Before 1845, the time in Manila,
the Philippines, was the same as Acapulco, Mexico, a discrepancy of
9h16m from Manila solar time.  This was a consequence of the Philippines
having been colonized and administered from Spanish America.  Nowadays the
standard time of Acapulco is UTC-6; of Manila, UTC+8.

Q: What happened in the Philippines on December 31, 1844?
A: Nothing.  It never existed.

--
John Cowan  [EMAIL PROTECTED]  http://ccil.org/~cowan
If I have not seen as far as others, it is because giants were standing
on my shoulders.
--Hal Abelson


Re: building consensus

2006-06-05 Thread John Cowan
Rob Seaman scripsit:

 One might suggest that the accommodation between civil time and legal
 time is of more interest.

I'm not sure what you mean by civil time in this context.  For some
people, civil time is synonymous with standard time; for others, it
means the time shown by accurate clocks in the locality.  I try to
avoid it, therefore.

 The sun certainly came
 up on that day and rose the following day about 24 hours later.

Yes, but the day was labeled 1845-01-01 and the following day
was labeled 1845-01-02.  There was no day labeled 1845-12-31 in
the Philippines.  Consequently, the year 1844 had only 365 days
there, and the last week of 1845 lacked a Wednesday.

This was not a calendar transition, but a (drastic) time zone transition
involving moving the International Date Line to the east.   (The IDL at
sea is a de jure line, but on land it is de facto and dependent on the
local times chosen by the various nations.)

 When they did that, what did they call it?  The day after December
 30, 1844?  Next Tuesday?  (Which begs the question, of course.)

They called it New Year's Day or January 1, 1845 (in Spanish).

 In any event, the case you are basically making is that in throwing
 off the yoke of their colonial masters, the Philippines specifically
 chose that their legal time should match their civil time and that
 their civil time should agree with local solar time.

Not at all and by no means.  Rather, it was Spanish America that had
ceased to be part of Spain; the Philippines switched to Asian time
because they were still a colony (and remained a Spanish colony until
1898 and an American one until 1946) and were no longer trading heavily
with the Americas; most of their trade was with the Dutch East Indies
and China, and it was commercially useful to share the same day.

--
Is a chair finely made tragic or comic? Is the  John Cowan
portrait of Mona Lisa good if I desire to see   [EMAIL PROTECTED]
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epical or dramatic?  If a man hacking in fury
at a block of wood make there an image of a cow,
is that image a work of art? If not, why not?   --Stephen Dedalus


Re: building consensus

2006-06-05 Thread John Cowan
Rob Seaman scripsit:

 I presume you aren't asserting that standard time clocks can't be
 accurate, but rather distinguishing between standard (timezone)
 time and local mean solar time?

No, I am reflecting the fact that some people define local civil time
in such a way as to exclude daylight-saving shifts.

 On the other hand, all I've ever meant by the term civil time is
 that time that a well educated civilian sets her clock in order to
 agree with other civilians for civilian purposes.

Good.  That is what I mean also.

 Interesting question:  On similar historical occasions, for instance
 during the transition from old style to new style dates as the
 Julian calendar gave way to the Gregorian, has the sequence of days
 of the week remained unbroken?  Or rather, have days of the week been
 skipped as well as days of the month?  Surely the Gregorian calendar
 is not just a rule for adding a leap day every four years (except
 sometimes), but also includes the definitions of the twelve months,
 and an initialization of a specific day-of-the-week on whatever date.

During the British transition, at least, the days of the week continued
their accustomed rotation.  I believe this was true of every such
transition as well.  Even while part of Europe was Gregorian and part
Julian, they all agreed on when Sunday was, most fortunately.

 This was not a calendar transition, but a (drastic) time zone
 transition involving moving the International Date Line to the east.

 Not obvious that there is any difference - kind of a calendrical
 Mach's Principle.

It is precisely the fact that there was no Wednesday in the Philippines
in that final week of 1845 that made it a time-zone rather than a
calendrical transition.

--
John Cowan  [EMAIL PROTECTED]  http://ccil.org/~cowan
If he has seen farther than others,
it is because he is standing on a stack of dwarves.
--Mike Champion, describing Tim Berners-Lee (adapted)


Re: building consensus

2006-06-05 Thread John Cowan
Mark Calabretta scripsit:

 You will find December 31, 1844 in both timescales.

All your points are correct, but it doesn't change the fact that
there was no 1845-12-31 in Manila, any more than there was a
second labeled 2006-04-02T00:02:30 in New York.

--
Evolutionary psychology is the theory   John Cowan
that men are nothing but horn-dogs, http://www.ccil.org/~cowan
and that women only want them for their money.  [EMAIL PROTECTED]
--Susan McCarthy (adapted)


Re: building consensus

2006-06-04 Thread John Cowan
Zefram scripsit:

 If this means that leap seconds and leap days are analogous, then I
 suppose so.  If it means something else, I don't understand it.

 That's what I meant.  Can you suggest a clearer wording?

Leap seconds (after 1972) are closely analogous to leap days.

 Being ambiguous between adjacent seconds seems inherently faulty to me.

The designers of Posix time thought it was more important to preserve
the property that dividing the difference between two time_t values
by 60, 3600, 86400 would give minutes, hours, days.

 Are you thinking of linear counts such as POSIX time, where the
 representation is ambiguous?  I was implicitly excluding those, on the
 grounds that they don't count as a representation.  It's also not
 linear.

No, it isn't.  But that doesn't mean you *can't* construct a numerical
representation of UTC time: say, the number of UTC seconds since
1972-01-01T00:00:00Z.

 Unix time (better: Posix time) *is* monotonically nondecreasing,
 provided you set it with NTP and not by brute force.

 Not necessarily.  The Mills kernel model makes the Unix time perform a
 backward step of 1 s during a positive leap second, and does so using
 data supplied by NTP.  I've seen Linux 2.4 perform this step (but during
 a simulated leap second, not a real one) in the course of testing some
 of my timekeeping code.

Quite so; my error.

--
John Cowan  http://ccil.org/~cowan[EMAIL PROTECTED]
There are books that are at once excellent and boring.  Those that at
once leap to the mind are Thoreau's Walden, Emerson's Essays, George
Eliot's Adam Bede, and Landor's Dialogues.  --Somerset Maugham


Re: building consensus

2006-06-01 Thread John Cowan
M. Warner Losh scripsit:

 In message: [EMAIL PROTECTED]
 Rob Seaman [EMAIL PROTECTED] writes:
 : Actually, this list is not a discussion per se.  If we simplify the
 : positions - just for the sake of argument here - to leap second yes
 : and leap second no, the reality is that the folks pushing the leap
 : second no position have never engaged with this list.  There are
 : several doughty people here who happen to have that opinion, but they
 : abide with us mortals outside the time lords' hushed inner sanctum.

 What an amaizingly unhelpful and offsensive statement.  I have spent
 much time explaining why leap seconds cause real problems in real
 applications, only to be insulted like this.

I believe you have misread Rob's remark, though I concede that it was
easy to misread.  I believe Rob meant that the people who are pushing
leap seconds no in *official* channels are not to be found on this list.
That being so, the leap seconds yes folks are unable to challenge them
or persuade them otherwise.

You and I, on the other hand, fall into the doughty people here group.

--
Is a chair finely made tragic or comic? Is the  John Cowan
portrait of Mona Lisa good if I desire to see   [EMAIL PROTECTED]
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epical or dramatic?  If a man hacking in fury
at a block of wood make there an image of a cow,
is that image a work of art? If not, why not?   --Stephen Dedalus


Re: Precision vs. resolution

2006-06-01 Thread John Cowan
Rob Seaman scripsit:

 Interesting question.  Perhaps it is the distinction between
 addressability and physical pixels that one encounters on image
 displays and hardcopy devices?  (Still have to posit which is which
 in that case :-)

Thanks to those who responded either publicly or privately.  In summary,
infinite are the arguments of mages.  Some take resolution to be a
near-synonym for precision, some take it to be a synonym for granularity.
The more definitive the source, the vaguer the definitions.

I should perhaps explain that I was interested in an internal
representation for durations, which I am now representing as a triple of
months, minutes, and seconds (the number of minutes in a month is not
predictable, nor the number of seconds in a minute given leap seconds,
but all other relationships are predictable:  10080 minutes/week, 12
months/year, 100 years/century, etc.)  To this I would add a fourth
nonnegative integer representing clock resolution units and wanted to
make sure I had the terminology correct.

Ah well.

--
John Cowan  [EMAIL PROTECTED]  http://ccil.org/~cowan
In the sciences, we are now uniquely privileged to sit side by side
with the giants on whose shoulders we stand.
--Gerald Holton


Precision vs. resolution

2006-05-24 Thread John Cowan
Can someone lay out for me exactly what the difference is between
clock precision and clock resolution?  I've read the NTP FAQ and
several other pages but am more confused than ever.

(I do understand the distinction between precision and accuracy:
3.1429493 is \pi precise to 8 significant digits, but accurate
only to 3.)

Thanks.

--
Values of beeta will give rise to dom!  John Cowan
(5th/6th edition 'mv' said this if you triedhttp://www.ccil.org/~cowan
to rename '.' or '..' entries; see  [EMAIL PROTECTED]
http://cm.bell-labs.com/cm/cs/who/dmr/odd.html)


Re: 24:00 versus 00:00

2006-02-17 Thread John Cowan
Ed Davies scripsit:

 No, it amounts to saying that some days are 24 hours and 1 second
 long.  When you're half a second from the end of such a day you
 are 24 hours, zero minutes and half a second from the start.

I grant that.  Nonetheless, the third-from-last figure in a broken-out
timestamp reflects the hour number, and by your scheme there would be
25 possibilities for its value, just as by the standard scheme there
are 61 possibilities for the second number.

 If you had a 1'6 piece of string you wouldn't say it's a two
 foot piece of string but the second foot is only 152.4 mm long.
 (Well, I think you wouldn't, though I think some politicians
 might.)

No, I wouldn't.  But in labeling every point on the string to a
precision of 1 inch, I would say that there are two possibilities
for the number of feet, 0 or 1.

--
John Cowan  [EMAIL PROTECTED]  www.ccil.org/~cowan  www.ap.org
If I have seen farther than others, it is because I was standing on
the shoulders of giants.
--Isaac Newton


Re: 24:00 versus 00:00

2006-02-16 Thread John Cowan
Ed Davies scripsit:

 If only the 24:00 for end of day notation wasn't in the way
 we could look at positive leap seconds as just being the
 result of deeming certain days to be a second longer than
 most and just use 24:00:00.  We wouldn't have to muck with
 the lengths of any of the hours or minutes within that day.

That amounts to saying that some days have 24 hours, whereas others
have 25 hours, 24 of them being 3600 seconds long and the 25th being
1 second long.  IMHO that is worse.

--
John Cowan  www.ccil.org/~cowan  www.ap.org  [EMAIL PROTECTED]
[T]here is a Darwinian explanation for the refusal to accept Darwin.
Given the very pessimistic conclusions about moral purpose to which his
theory drives us, and given the importance of a sense of moral purpose
in helping us cope with life, a refusal to believe Darwin's theory may
have important survival value. --Ian Johnston


Re: Accommodating both camps

2006-01-25 Thread John Cowan
Warner Losh scripsit:

 This is the biggest misunderstanding [...] an hour off of solar time.

I now abbreviate this whole argument with the word Kashi.
(To reiterate: |LMT-LCT| in Kashi, a city in western China (which has
no DST), is about 3 hours.)

 But again, giving up leap seconds in UTC is not the same as
 accepting atomic time as civil time.

 Again, I don't quite understand this statement.  Can you elaberate a
 bit on the difference?

I don't think anyone in the plan #2 camp wants to change UTC as such:
some people find it useful.  What we want, I think (or at least what
I want) is to make TI rather than UTC the foundation of legal local time.

--
Well, I'm back.  --SamJohn Cowan [EMAIL PROTECTED]


Re: Risks of change to UTC

2006-01-23 Thread John Cowan
Clive D.W. Feather scripsit:

 Why not? Greek and Latin, to name two, were spoken that long ago and are
 recognisable today.

Indeed, and they passed through a far tighter bottleneck than anything
likely today.

Not even the most diligently destructive barbarian can
extirpate the written word from a culture wherein the
*minimum* edition of most books is fifteen hundred
copies.  There are simply too many books.
--L. Sprague de Camp, _Lest Darkness Fall_

 And the English of 1000 years ago is still an official language of the
 Netherlands (under the name Frisian).

Bread, butter, and green cheese / Is good English and good Friese.
Brea, bûter, en griene tsiis / Is goed Ingelsk en goed Frysk.

(That û is u-circumflex, in case of encoding problems.)

--
Long-short-short, long-short-short / Dactyls in dimeter,
Verse form with choriambs / (Masculine rhyme):  [EMAIL PROTECTED]
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Challenges poets who / Don't have the time. --robison who's at texas dot net


Re: the tail wags the dog

2006-01-23 Thread John Cowan
Rob Seaman scripsit:

 The legal time in the US is the mean solar time at a given
 meridian, as determined by the secretary of commerce

 ...and many may have seen Mr. Gutierrez shooting the sun with his
 sextant out on the Mall in front of the AS Museum :-)

 With all the words that have flowed over the spillway, I'm not sure
 the point has been made that a feature of solar time is precisely
 that it can be reliably recovered from observations whenever and
 wherever needed (once you are located with respect to a meridian, of
 course).

I don't understand this.  You can't shoot the mean sun with a sextant,
only the friendly (apparent, whatever) sun.  So at the very least
you need an analemma.

In any case, the majority of the world has managed to live with the fact
that the day-of-month can no longer be recovered by examining the moon,
although if we were still hunter-gatherers a purely lunar calendar would
make a lot of sense.

--
XQuery Blueberry DOMJohn Cowan
Entity parser dot-com   [EMAIL PROTECTED]
Abstract schemata   http://www.reutershealth.com
XPointer errata http://www.ccil.org/~cowan
Infoset Unicode BOM --Richard Tobin


Re: Risks of change to UTC

2006-01-20 Thread John Cowan
Rob Seaman scripsit:

 Only a minority (small minority, one would think) of
 systems currently include any DUT1 correction at all - although these
 will perhaps tend to be the most safety-critical applications.  [...]

 That is, of course, one of the major issues for astronomers - we rely
 on UTC providing a 0.9s approximation to UT1 and most of our systems
 don't use DUT1.  Even our high precision applications (in either
 interval or universal time) don't tend to require conversions other
 than as a preprocessing step.  Remediating our systems for such a
 fundamental change to UTC would involve much larger changes than Y2K
 did - algorithms and data structures would have to change, not just
 the width of some string fields and sprinkling some 1900's around.

I don't understand this.  The first class of applications, those
that actually receive DUT1 from somewhere, probably have a hard-coded
assumption that |DUT1| never exceeds 0.9s or at worst 1.0s.  They would
need remediation.  The second class, which just assumes UTC = UT1
and doesn't care about subsecond precision, would simply need to be
front-ended with a routine that got DUT1 from somewhere and mixed it
with TI to generate their own UT1.  This is technically remediation,
but of a rather black-box kind.

 Also, standalone applications would have to become network aware to
 have access to externally derived tables of DUT1.

Well, this is perhaps no worse than systems that now have access to UTC
and want reliable interval time needing externally derived tables of
leap seconds.

 Astronomers might be unusual in needing to introduce DUT1 into our
 systems (on a short schedule for a large expense) should Sauron win
 and the nature of UTC change, but we wouldn't be alone.  And as clock
 time diverges further and further from solar time, more systems in
 more communities (transportation, GIS, innumerable scientific
 disciplines, what have you) would be revealed to need remediation.

Can you spell out some of those implications?

--
What has four pairs of pants, lives John Cowan
in Philadelphia, and it never rains http://www.reutershealth.com
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Re: Risks of change to UTC

2006-01-20 Thread John Cowan
Neal McBurnett scripsit:

 To sum it up, PLEASE don't fundamentally change the DEFINITION of UTC,
 or you risk whole new kinds of confusion.  Hopefully by now the folks
 on this list that don't like leap seconds at least have agreed that
 any change should be to a new time scale like TI, and announced
 decades in advance.

I certainly do, and I hope everyone else who is down-leaps does too.
TI is a good name (you can read it as TAI - A where A is a constant
to be decided when the scale is inaugurated).

--
John Cowan  www.ccil.org/~cowan  www.reutershealth.com  [EMAIL PROTECTED]
[T]here is a Darwinian explanation for the refusal to accept Darwin.
Given the very pessimistic conclusions about moral purpose to which his
theory drives us, and given the importance of a sense of moral purpose
in helping us cope with life, a refusal to believe Darwin's theory may
have important survival value. --Ian Johnston


Re: Risks of change to UTC

2006-01-20 Thread John Cowan
James Maynard scripsit:

 Small boats, sea water, and electrical systems don't mix very well. The
 damp, salty environment all too often leads to failures of a boat's
 electrical system.  A prudent sailor should not rely for navigation only
 on electrically powered systems like GPS or loran.

Your points are excellent, although it seems to me that a wind-up GPS
receiver is a possibility.

 But if UTC is allowed to drift away from UT1 by eliminating leap
 seconds, celestial navigation fixes will become less and less useful. A
 time error of half an hour in UT1 equates about to 450 NM at the equator.

Navigators are clearly people who would need access to |TI-UT1| along with
astronomers, yes.

--
John Cowan  www.ccil.org/~cowan  www.reutershealth.com  [EMAIL PROTECTED]
Mr. Henry James writes fiction as if it were a painful duty.  --Oscar Wilde


Re: Monsters from the id

2006-01-15 Thread John Cowan
Mark Calabretta scripsit:

 If you go through the exercise trying to tie leap hours to DST, as I
 challenged, you will discover that it raises many questions that are not
 addressed by the leap hour proposal.

I realize the ALHP has severe problems with this, but I don't approve
of the ALHP anyhow (save perhaps tactically, as explained).

 If you make some plausible assumptions as to how it would operate, with
 DST starting and ending at the usual times of year and leap hours
 occurring on new year's eve, I believe you will find it far from simple
 to do in a rigorous fashion, and that at least one of the timescales is
 genuinely discontinuous.

Indeed.  But the sensible approach would be for each State government to
fail to omit the hour of the normal spring transition in the year 2700,
say.  In that way, AEDT would become TI+1000 and a normal-looking autumn
transition would cause AEST to become TI+0900.  Countries without DST
transitions would have to actually repeat an hour, of course, just
as Algeria had to do in 1940, 1956, 1977, and 1981 (the country has
repeatedly flipflopped between UTC+ and UTC+0100).

By the way, I re-counted all the secular time zone transitions worldwide.
According to the Olson timezone database, there have been 516 of them
since the beginning of standard time (when that is, of course, varies
with the country or subdivision thereof).

--
John Cowan  http://www.ccil.org/~cowan  [EMAIL PROTECTED]
Be yourself.  Especially do not feign a working knowledge of RDF where
no such knowledge exists.  Neither be cynical about RELAX NG; for in
the face of all aridity and disenchantment in the world of markup,
James Clark is as perennial as the grass.  --DeXiderata, Sean McGrath


Re: Problems with GLONASS Raw Receiver Data at Start of New Year

2006-01-14 Thread John Cowan
Rob Seaman scripsit:

 But there are also risks associated with *not* having
 leap seconds, with allowing DUT1 to increase beyond 0.9s, for
 instance.  And events triggered by those risks would not draw
 worldwide scrutiny - they could occur year-round and the media circus
 would have moved on.

I'd expect to see a wave of breakage as DUT1 exceeded 0.9s for the first
time, and a second wave as it exceeded 1s for the first time.  After
that, of course, the problems would no longer be relevant.  :-)

--
They tried to pierce your heart John Cowan
with a Morgul-knife that remains in the http://www.ccil.org/~cowan
wound.  If they had succeeded, you wouldhttp://www.reutershealth.com
become a wraith under the domination of the Dark Lord. --Gandalf


Re: Monsters from the id

2006-01-12 Thread John Cowan
Rob Seaman scripsit:

 I went rummaging through the ITU proposal and back as far as Torino.
 Found this comment from a LEAPSECS thread on 28 July 2003:

  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.

This is definitely the PHK/JWC proposal rather than the ALHP: civil time
refers to local legal/business time.

 The difference of UT1 from UTC should not exceed ±1h.

This, however, clearly is the ALHP.

 The point I was trying to make is that you can't simultaneously omit
 the overlaps/gaps and preserve anything even vaguely resembling the
 familiar relationship between our clocks and the solar day.

The relationship between our clocks (legal time clocks, the only kind
I am concerned with) and the solar day is very weak, as I have established
over and over.  If local  is the middle of the night, the practical
requirements of legal time are pretty much satisfied.

 people everywhere in the world
 would  have to deal with the repercussions.  That the situation will
 degrade slowly over a few hundred years before collapsing
 catastrophically doesn't really seem to recommend the plan.

There will be no catastrophic collapse, just a gradual local adjustment
as needed.

 It may not sound like it, but I am willing to be convinced otherwise
 - but you'll have to do a lot better than rivaling the scant length
 of the ITU proposal.  How about a detailed scenario of exactly how
 you see this working for a couple of neighboring but distinct local
 timezones?  What is the precise mechanism that might be used?

A sovereign country will notice that there is too much discrepancy
between solar time and legal time to be comfortable: perhaps kids are
waiting for school buses in the dark, as happened in the U.S. in 1974.
The country will then adjust its legal time, perhaps in coordination
with its neighbors, perhaps not.

 The subtext of both your position and the absurd leap hour proposal
 is that civil timekeeping is so trivial that everybody from barbers
 to burghermeisters should be encouraged to make public policy - after
 all, these aren't important scientific and technical issues.

Those who want UT1 or TAI know where to get it.

 Rather, civilian users deserve as good or better a timescale as the
 technical users (who ultimately can take care of themselves).

Good for what?  (This is not a rhetorical question.)

 Aliens?  Us?  Is this one of your Earth jokes?

No.

--
John Cowan  [EMAIL PROTECTED]  www.reutershealth.com  www.ccil.org/~cowan
The known is finite, the unknown infinite; intellectually we stand
on an islet in the midst of an illimitable ocean of inexplicability.
Our business in every generation is to reclaim a little more land,
to add something to the extent and the solidity of our possessions.
--Thomas Henry Huxley


Re: Monsters from the id

2006-01-12 Thread John Cowan
Rob Seaman scripsit:

 And the point I'm making is that you can't shift timezones at will to
 accomplish this without creating seams in legally realized time.

We already have seams in legally recognized time.

 Just making the dark stay put would result in ambiguous
 timekeeping.  Daylight saving time layered on solar locked standard
 time is a different thing from attempting to use an overtly similar
 mechanism to compensate for the misappropriate substitution of
 interval time for solar time.

Stripped of the adjectives, why is it different?

 What starts out as gradual (also known as ignored completely)
 will end in the same familiar quadratic rush.  Nothing about your
 notion mitigates this.

In the end, it will be impossible to maintain the notion that a solar
day is 24h of 60m of 60s each: we wind up, IIRC, with the solar day
and lunar month both at about 47 current solar days.

 1) provide a system for uniquely sequencing historical events

Haven't got that now.

 2) allow events in distant lands to be compared for simultaneity

We have that now, but it takes a computer to keep track of all the
details in the general case.

 3) avoid disputes over contractual obligations

That's done by specifying the legal time of a given place.  If I agree
to meet you under the Waverley at noon 13 March 2020, it's all
about what the U.S. Congress says legal time in New York City is
as of that date -- which is not predictable in advance.  (You will also
have a problem finding the Waverley, unless you are an old New Yorker.)

 4) minimize the potential for political disagreements

Good luck.

 5) satisfy religious requirements

Out of scope.

 6) keep it dark near 00:00 and light near 12:00

Agreed.

 7) support educational goals (Yes Virginia, the universe actually
 makes sense.)

No problem.

 8) allow coal miners to aspire to be amateur astronomers

Eh?  I am not recommending abolishing UT1, though it seems strange to
me to measure angles in hours, minutes, and seconds instead of in
radians like a proper SI-head.  (Fourteen inches to the pound, oh Bog!)

 9) permit the construction of sundials - public clocks with no moving
 parts

Sundials don't show legal time or even a good approximation of it much
of the time.

 10) tie an individual's first breathe on her first day to her last
 breathe on her last day

Where's the problem here?  Any timescale can do that, even the Mayan Long Count.

--
John Cowan  [EMAIL PROTECTED]  www.reutershealth.com  www.ccil.org/~cowan
The whole of Gaul is quartered into three halves.
-- Julius Caesar


Re: War of the Worlds

2006-01-11 Thread John Cowan
Rob Seaman scripsit:

 I don't have an envelope large enough, but there are various issues
 to consider.  The Hurtling Moons of Barsoom are much smaller than our
 own and should have a negligible tidal breaking effect.  (See http://
 www.freemars.org/mars/marssys.html, for instance, for their
 interesting history.)  And do the Earth's oceans mediate our Moon's
 breaking or is that a crustal phenomenon?  (The Earth-Moon system
 should better be regarded as a double planet, than planet and
 satellite.)  On the other hand, Mars passes much closer to Jupiter,
 the 800 pound gorilla of the solar system, but then it is further
 from King Kong - the Sun, that is - and tides are an inverse cube
 effect.  But Mars is much smaller and has a smaller moment of inertia
 in the first place - but then Mars is much smaller and the lever
 arm to grapple with it is less pronounced.

 Taken all together, one suspects that LOD(Mars) is many orders of
 magnitude more constant than LOD(Earth).  One would not be
 flabbergasted to be utterly wrong, however.

I wouldn't be too quick to dismiss tidal braking from Phobos.  It's
awfully close to Mars, and tidal braking is as you say an inverse-cube
effect.  The formula (kai Wikipedia) is (2GMmr)/R^3, where M and m are
the masses, r is the radius of the primary, and R is the orbital radius
of the secondary.  The mass of the Earth-Moon system is eight orders of
magnitude larger than the Mars-Phobos system, and the radius of Earth
is only twice the radius of Mars, but the ratio of the cubed orbital
radii is five orders larger for Phobos than for the Moon.  So the tidal
acceleration of the Moon toward the Earth is only some three orders larger
than Phobos's toward Mars.  That puts the effect in the same ballpark.
How much difference in actual slowing can be attributed to Earth's ocean
and Mars's lack of one I don't know.

(See http://www.madsci.org/posts/archives/oct98/908453811.As.r.html for
the relevant masses and radii.)

--
Eric Raymond is the Margaret Mead   John Cowan
of the Open Source movement.[EMAIL PROTECTED]
--Bruce Perens, http://www.ccil.org/~cowan
  some years agohttp://www.reutershealth.com


Re: War of the Worlds

2006-01-11 Thread John Cowan
Neal McBurnett scripsit:

  I wouldn't be too quick to dismiss tidal braking from Phobos.  It's
  awfully close to Mars, and tidal braking is as you say an inverse-cube
  effect.  The formula (kai Wikipedia) is (2GMmr)/R^3, where M and m are
  the masses, r is the radius of the primary, and R is the orbital radius
  of the secondary.  The mass of the Earth-Moon system is eight orders of
  magnitude larger than the Mars-Phobos system, and the radius of Earth

 I assume you mean the mass of phobos vs the mass of the moon, not the
 systems, since that is what fits in the raw numbers and equations you
 provide.  But that is less than 7 orders of magnitude different, as I
 read your reference.

Actually I didn't mean either one: I meant the mass of the primary times
(not plus) the mass of the secondary, the Mm in the formula.  So
the mass of Mars times the mass of the Phobos is ~ 10^39 kg, whereas
the mass of Earth times the mass of the Moon is ~ 10^47 kg:  eight
orders of magnitude, as I said.  Sorry for the misstatement.

--
Even a refrigerator can conform to the XML  John Cowan
Infoset, as long as it has a door sticker   [EMAIL PROTECTED]
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--Eve Maler http://www.ccil.org/~cowan


Re: The real problem with leap seconds

2006-01-10 Thread John Cowan
Tim Shepard scripsit:

[many sensible opinions snipped]

 leap hours are a horrible idea, whether they be leap hours inserted
 in to some UTC-like global standard, or by local jurisdictions.

I understand what's wrong with the former kind, but what's wrong with
the latter?  Why do you think they are more of a problem than DST shifts?

--
Andrew Watt on Microsoft:   John Cowan
Never in the field of human  computing  [EMAIL PROTECTED]
has so much been paid by so manyhttp://www.ccil.org/~cowan
to so few! (pace Winston Churchill) http://www.reutershealth.com


Re: interoperability

2006-01-09 Thread John Cowan
Rob Seaman scripsit:

 This is like the day is light and night is dark statement: there
 is, at any given location, one and only one sunrise per (solar)
 day, no matter what clocks say.

 Communication prospers when people's clear meaning is not subjugated
 to petty grammarians.

My point was that your rhetorical flourishes have run away with you
on more than one occasion.

 We are now - and have been - discussing timekeeping changes that call
 into question the definition of a day.  Those of us who support
 solar time are fundamentally asserting the primacy of the the
 standard day over the standard second (for civil timekeeping
 purposes).  Those of us who consider solar time to be a curious
 anachronism, assert the the SI second over the concept of a day (for
 civil timekeeping purposes).

I agree with this assessment, more or less.

 As I've pointed out before, future times in legal documents are
 defined as LCT for a particular place, since the future mapping
 between LCT and any other time scale is not known.

 At the risk of igniting a new round of stage two nonsense, consider
 the implications of your statement.  Currently LCT (as you appear to
 mean it) is standard time.  Daylight saving (under whatever name) is
 merely an overlay on standard time.  Standard time has no jumps
 (except for leap seconds).

 Under your suggestion, LCT would include the jumps for daylight
 saving time (if locally used) as well as the jumps to correct for the
 cumulative effect of tidal slowing.  As I hope I have established,
 these are fall back discontinuities that would result in the same
 hour of LCT occurring twice.  Is this not perceived to be a problem?

Perhaps the problem here *is* merely semantic.  By LCT I mean legal
time, the time that de jure or de facto is observed in any given place
(New York time in New York, Podunk time in Podunk, and Squeedunk time
in Squeedunk).  That includes all periodic or secular changes.
And although periodic changes are far more common, secular changes
for reasons of public convenience are *far* from unknown.

I will try to say legal time from now on, though there are parts of
the world (Antarctica, the oceans) where there is no legal time
strictly speaking, and de facto time rules.

It *is* a problem that some instants of (TAI/UTC) time have the same
LCT labels in certain time zones.  But it's a problem that we already
deal with once a year.  TV stations, for example, normally broadcast
the same program twice in a row on Leapback Sunday, at least in the U.S.

--
John Cowan  [EMAIL PROTECTED]  www.ccil.org/~cowan  www.reutershealth.com
The penguin geeks is happy / As under the waves they lark
The closed-source geeks ain't happy / They sad cause they in the dark
But geeks in the dark is lucky / They in for a worser treat
One day when the Borg go belly-up / Guess who wind up on the street.


Re: interoperability

2006-01-08 Thread John Cowan
Rob Seaman scripsit:

 The question is:  how precisely does this differ from the situation
 now or in the past?  Whether by fiat or not, some common worldwide
 stage two clock must exist.

Again, no it doesn't need to exist.

We need a uniform time scale like TAI.  And we need local civil time
for all the 400-odd jurisdictions in the world today.  If other people
need other timescales (and they do), there's no reason that should
affect the two requirements above.

 But how in practice is it envisaged that a scheme
 for migrating time zones versus TAI would work, precisely?

Straightforwardly.  Each locality decides when and how to adjust both
its offset from TAI and its seasonal transition function (if any),
just as it does today.  What we abandon is a universal time tightly
synchronized to Earth rotation in favor of a universal time
independent of earth rotation plus 400+ local civil times roughly
synchronized to Earth rotation containing various glitches.

--
We pledge allegiance to the penguin John Cowan
and to the intellectual property regime [EMAIL PROTECTED]
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Re: interoperability

2006-01-08 Thread John Cowan
Rob Seaman scripsit:

 Sure, and you can timestamp then on either timescale, because there
 is a 1 to 1 translation between the two timescales [1].

 Perhaps I miss your meaning here, too.  The event of migrating a time
 zone is a discontinuity just as with a leap second or leap hour.

Sure.  But discontinuities in LCTs are something we already know how to handle.

 This is true.  It is irrelevant to the underlying international
 clock.

PHK and I are denying any need for an international clock that tracks
Earth rotation.

 What matters is not when sunrise occurs, but rather that every day
 has one (and only one).

This is like the day is light and night is dark statement: there is,
at any given location, one and only one sunrise per (solar) day,
no matter what clocks say.

 Exactly.  The pressures to maintain a common international vision of
 time will trump local variations.  It is the resulting common
 international  time clock that you won't let me refer to as civil
 time.  All requirements placed on UTC flow backwards from here.  You
 can't just edit UTC (or GMT) out of the debate.

What common international vision of time?  There is no common international
LCT.

stage one is atomic time (e.g., TAI)
stage two is international civil time (e.g., UTC)
stage three is local legal time (e.g., Mountain Standard Time)

What we are looking for is to redefine stage three directly in terms of
stage one without regard to a factitious stage two.

 In a couple of hundred years, the Danish Parliament (or its
 successor in interest) will simply decide from -MM-DD HH:00,
 the Danish Civil time will use offsets -3h and -2h (instead of
 presently -1h/-2h) and the transition will happen on the switch
 from summertime to wintertime by _not_ adjusting the clock.

 The only way this differs from the leap hour proposal is that you are
 assuming that different localities can (or would) carry these
 adjustments out separately.

Exactly!  That is what the principle of subsidiarity demands, and it is
a situation we already know how to handle.

 A fall back event means that the clock (local, standard,
 international, whatever clock you want) first traverses an hour - and
 then traverses it again.  Under the current three stage system it is
 only the most local stage three clocks that are affected.  You are,
 in effect, promoting this discontinuity to stage two - to the
 worldwide business timescale.  More to the point, you have said that
 stage one can be mapped back-and-forth to stage two.  But we've just
 shown that this is no longer a one-to-one mapping since the hour is
 traversed twice, corresponding to two hours of TAI duration.

You've redefined stage two in the course of this discussion.  Before it
meant LCT, now it means UTC.  But be that as it may.

Since we (PHK and I) are in favor of abolishing stage two, we are not
promoting the discontinuity from stage three to stage two.  Rather, we are
interested in allowing the various local authorities to introduce changes
into their stage three clocks *as they decide* to deal with any perceived
problems.

The true leap hour folks, if any, are actually doing what you say we are
doing: creating a large discontinuity in stage two.  The fake leap hour
folks, if any, are actually doing what we want, but are cynically saying
there will be a leap hour in stage two while not expecting such a thing
to ever happen.

 Ah!  But you've suggested that the other half of the annual daylight
 saving pendulum be used.  This doesn't work because we're on the
 wrong side of the pendulum's arc.  The point being that you don't
 need to *not* adjust the clock in the Autumn - you need to not adjust
 the clock in the Spring.  It is the springtime gap in the mapping
 (also not a very desirable feature for a time scale) that is omitted
 during one of these events - not the harvest-time doubly traversed hour.

Fair enough.

 (We'll omit discussion of the fact that not all localities observe
 daylight saving time in the first place.)

By all means.  (This is the rhetorical figure of *praeteritio*.)

 This is the same point I was trying to make about the 25 hour day.
 No historian or lawyer is going to look favorably on a situation that
 results in ambiguous timestamps.  Perhaps, you say, such timestamps
 should all be kept in TAI.  But in that case, we are back to the
 original question of why a stage two clock is needed at all.  By
 asserting stage two is needed, all the rest logically follows.

And we assert that stage two is *not* needed.  In any case, most of the
world's population deals with ambiguous timestamps every year.

As I've pointed out before, future times in legal documents are defined
as LCT for a particular place, since the future mapping between LCT and any
other time scale is not known.  This turns out not to be a big problem,
except for the makers of calendar programs.

--
John Cowan  http://www.ccil.org/~cowan  [EMAIL PROTECTED]
Be yourself

Re: interoperability

2006-01-08 Thread John Cowan
Poul-Henning Kamp scripsit:

 Windows have got it right now I belive, but it used to be that a
 file created and transmitted from Denmark at the end of the business
 day would be older than a file created at the start of business day
 in California, despite a strict ordering of the events.

It's still true in the sense that the hardware clock is assumed to run
in LCT on Windows, and therefore discovering UTC depends on a correctly
set TZ variable.  It's false in the sense that Windows now supports TZ
correctly.

 Sure, and you can timestamp then on either timescale, because there
 is a 1 to 1 translation between the two timescales [1].

I think it's confusing to call it 1 to 1, except in the sense that
LCT seconds are the same length as UTC/TAI seconds.  There are many
LCT timestamps that correspond to more than one UTC timestamp.
This can be kludged around by adding a bit (the isdst field in a struct time)
to say whether a LCT timestamp is the first or the second instance.

 The scheme you propose is eminently workable, and more or less exactly
 what we advocate.  I'm happy that you now see the merits of it.

Nope, he still doesn't.

--
On the Semantic Web, it's too hard to prove John Cowan[EMAIL PROTECTED]
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Re: The real problem with leap seconds

2006-01-07 Thread John Cowan
Ed Davies scripsit:

 (There's a small difference in practice in that the UTC to
 TAI conversion requires a lookup table which is not known
 very far into the future whereas the Gregorian calendar is
 defined algorithmically for all time.)

Well, yes.  But that's a matter of verbal labels.  The Gregorian calendar
extends to all future time: what is not known is the date on which it
will be replaced in civil use by a further refinement.  We know we will
need one eventually, both because of the current annual discrepancy of
about 27 seconds between the Gregorian and tropical years, and because
of future changes in the length of the tropical year.

--
John Cowan  [EMAIL PROTECTED]  www.reutershealth.com  www.ccil.org/~cowan
If a traveler were informed that such a man [as Lord John Russell] was
leader of the House of Commons, he may well begin to comprehend how the
Egyptians worshiped an insect.  --Benjamin Disraeli


Re: The opportunity of leap seconds

2006-01-07 Thread John Cowan
Rob Seaman scripsit:

 Unless we *completely* change our notion of Canoli, Canoli is tightly
 constrained to follow Eclair simply by the fact that today and
 tomorrow and the million days that follow are all required to be dark
 at night and light in the day.

I think you are getting carried away by your own rhetoric here.  It will
be dark at night and light in the daytime even if we smash every clock
on Earth (not a bad idea, I think sometimes).  What you surely mean
is that it should be locally dark when local clocks say  and thereabouts,
and consequently light when they say 1200 and thereabouts.  There is
much room for adjustment around the midpoints, however.

 Whether we choose to bleed off the
 daily accumulating milliseconds one second or 3600 at a time, bleed
 them we must...and even people who loathe the very notion of leap
 seconds admit this.

NO, I DON'T ADMIT THAT.  On the contrary, I deny it, flatly, roundly,
and absolutely.

 (The craven ITU proposal is obligated to pay lip
 service to leap hours, though what they really are saying is let's
 close our eyes and wish it away.)  Time to move on.

The leap-hour proposal can be read as either (a) a serious proposal to
inject an hour into UTC at some future date, or (b) a cynical proposal to
abandon leap seconds and not replace them.

I think (a) is just as foolish as leap seconds, if not more so.  As for
(b), it may be the best political approximation to what I really want,
which is (c): abandon leap seconds altogether.

But then, soon enough, it won't be dark at !  Yes it will, just
not in the skies over Greenwich.  Practical difficulties can be overcome
by making secular changes to the offsets between LCT and UTC, just as is
done today when such problems arise.  (In the next two years, the U.S.,
to name just one country, will make two secular changes to its LCT offsets.)

The computerniks of the world already know how to handle such things,
so future migrations will not be a problem.

And people who want, for their legitimate purposes, to have access to UT1
will have to get it some other way.

--
It was impossible to inveigle   John Cowan [EMAIL PROTECTED]
Georg Wilhelm Friedrich Hegel   http://www.ccil.org/~cowan
Into offering the slightest apology http://www.reutershealth.com
For his Phenomenology.  --W. H. Auden, from People (1953)


Re: The real problem with leap seconds

2006-01-07 Thread John Cowan
Steve Allen scripsit:

 The changes in the length of any kind of year are slight by comparison
 to the changes in length of day.  Neglecting short period variations
 the length of the sidereal year has not changed much in a billion years.

That is to say, the current best approximation to the n-body problem of
the Solar System says that it hasn't.  Fair enough.  I merely threw that in
in case it was an issue.

 The Gregorian calendar was designed to match the vernal equinox year.

Thanks for the correction.

 The new fields being added to GPS signals make them able to count leap
 seconds for 3 years.  That's quite an example of engineering margin.

Indeed.  But then so is IPv6 (if we ever get it adopted widely).

--
John Cowan  [EMAIL PROTECTED]  www.ccil.org/~cowan  www.reutershealth.com
In the sciences, we are now uniquely privileged to sit side by side
with the giants on whose shoulders we stand.
--Gerald Holton


Re: The opportunity of leap seconds

2006-01-07 Thread John Cowan
Poul-Henning Kamp scripsit:

 By your logic, the U.S. Surgeon General should be a chiropractor.

 Once the US government tries to shoulder their national deficit
 that would undoubtedly be a good idea.

Chiropractors are by no means cheaper to hire than other doctors.
Nor are their treatments necessarily the worse because their theory
is crappy.

 Light of day and darkness of night already is, and for all relevant
 future can be, assured by governmental adjustments of the two functions
 government control in the formula:

 Civil Time(time) = UTC(time) +
  TimeZoneOffset(country, subdivision, time) +
  SeasonalOffset(country, subdivision, time)

Indeed.  I did a quick look once at the number of secular changes to the
TimeZoneOffset function since the adoption of standard time in the
various countries; I may have posted the results here.  If not,
I'll try to dig them up.

--
John Cowan  [EMAIL PROTECTED]  www.reutershealth.com  www.ccil.org/~cowan
   There was an old manSaid with a laugh, I
 From Peru, whose lim'ricks all  Cut them in half, the pay is
   Look'd like haiku.  He  Much better for two.
 --Emmet O'Brien


Re: Longer leap second notice

2006-01-06 Thread John Cowan
Clive D.W. Feather scripsit:
 John Cowan said:
  Barry gules and argent of seven and six,John Cowan
  on a canton azure fifty molets of the second.   [EMAIL PROTECTED]
  --blazoning the U.S. flag   http://www.ccil.org/~cowan

 You don't get odd numbers of barry. It's Gules, six bars argent.

I have received comments to this effect, but also to the opposite effect.
In any case, the Great Seal of the United States is blazoned in the
enabling legislation [p]aleways of thirteen pieces, argent and gules,
which is certainly relevant precedent, since the even-only theory of
barry is also usually applied to paly.

Infinite are the arguments of mages.

--
One Word to write them all, John Cowan [EMAIL PROTECTED]
  One Access to find them,  http://www.reutershealth.com
One Excel to count them all,http://www.ccil.org/~cowan
  And thus to Windows bind them.--Mike Champion


Re: Longer leap second notice

2006-01-04 Thread John Cowan
Ed Davies scripsit:

 The main requirements for local civil time for the bulk of its
 users are that:

Agreed.

  1. local civil time matches apparent solar time roughly (e.g., the
 sun is pretty high in the sky at 12:00 and it's dark at 00:00).

I think the last is the important point, or more specifically that the
bulk of the population not begin work on one day and end on another
(astronomers excepted, of course).  This would be a bookkeeping nightmare.

--
Barry gules and argent of seven and six,John Cowan
on a canton azure fifty molets of the second.   [EMAIL PROTECTED]
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Re: GMT - UTC in Australia

2005-02-24 Thread John Cowan
Rob Seaman scripsit:

 Ad hoc is not a synonym for secular.  I'm pleased to see someone
 other than the astronomers in this conversation using the word secular,
 but there continues to be a fundamental confusion of Daylight Saving
 clock adjustments (periodic) with the silly notion of leap hours
 (fundamentally secular).

Not by me.  There have been genuinely secular changes in zone, call
them silly or not:  Pacific/Enderbury (Phoenix Islands Time) changed
its time zone from -11:00 to +13:00 in 1995, and Asia/Kashgar (extreme
western China) changed its time zone from -5:00 to -8:00 in 1980-05
(its LMT is 5:03:56).

 No reasonable standard can be based on constraining the behavior of our
 descendants 600 years hence.

They are only constrained in the sense that Pope Gregory was constrained
by the decisions of Julius Caesar.  By 2600 we may simply not care about
the apparent position of the sun (or anything else, perhaps).

--
John Cowan  [EMAIL PROTECTED]  www.reutershealth.com  www.ccil.org/~cowan
[R]eversing the apostolic precept to be all things to all men, I usually [before
Darwin] defended the tenability of the received doctrines, when I had to do
with the [evolution]ists; and stood up for the possibility of [evolution] among
the orthodox -- thereby, no doubt, increasing an already current, but quite
undeserved, reputation for needless combativeness.  --T. H. Huxley


Re: GMT - UTC in Australia

2005-02-24 Thread John Cowan
Tom Van Baak scripsit:

 Rob, this will always be true, won't it? Whether you
 have 100 ms time step adjustments, or 100 x e-10
 rate adjustments, leap seconds, or leap hours it
 seems to me there has been and will always be an
 honest attempt to coordinate the two scales.

No, no.  Leap hours are qualitatively different: they change the adjustment
between TAI and LCT, ignoring earth rotation altogether.

--
I marvel at the creature: so secret and John Cowan
so sly as he is, to come sporting in the pool   [EMAIL PROTECTED]
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Re: The Eleven Days

2005-01-27 Thread John Cowan
Clive D.W. Feather scripsit:

 See also http://www.davros.org/misc/easter.html and the Easter Act 1928.

Most interesting, and an excellent Web site.

--
[T]he Unicode Standard does not encode John Cowan
idiosyncratic, personal, novel, or private  http://www.ccil.org/~cowan
use characters, nor does it encode logoshttp://www.reutershealth.com
or graphics.   [EMAIL PROTECTED]


Re: two world clocks AND Time after Time

2005-01-24 Thread John Cowan
Steve Allen scripsit:

 What we are being told by the Time Lords is that, starting from a date
 in the near future, knowing when noon is will also be a specialist
 operation.

Already true.

For many months of the year, solar noon is closer to 1 PM, or even 1:30
PM, in a great many countries, and how many people actually realize
*that*?

--
Winter:  MIT,   John Cowan
Keio, INRIA,[EMAIL PROTECTED]
Issue lots of Drafts.   http://www.ccil.org/~cowan
So much more to understand! http://www.reutershealth.com
Might simplicity return?(A tanka, or extended haiku)


Re: Time after Time

2005-01-23 Thread John Cowan
Markus Kuhn scripsit:

 UTC currently certainly has *no* two 1-h leaps every year.

There seems to be persistent confusion on what is meant by the term
leap hour.  I understand it as a secular change to the various LCT offsets,
made either all at once (on 1 Jan 2600, say) or on an ad-lib basis.
You seem to be using it in the sense of a 1h secular change to universal
time (lower-case generic reference is intentional).

Can anyone quote chapter and verse from Torino to show exactly what was
meant?  Or is the text in fact ambiguous?

 If you read, just one example, to deviate a bit from the overwhelmingly
 US/UK-centricism of this legal argument,

I keep talking about the Chinese example.  Consider the city of Kashi,
population about 175,000.  Its longitude is about 76 E, which means
that its LMT is about GMT+5.  Its LCT, however, is Asia/Shanghai, or
UTC+8.  If all those people can live with an LCT that is three hours
away from the sun, we can stand rather lower discrepancies just fine.

--
Don't be so humble.  You're not that great. John Cowan
--Golda Meir[EMAIL PROTECTED]


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 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


Re: two world clocks

2005-01-20 Thread John Cowan
Rob Seaman scripsit:

 What exact future systems are we discussing that will both 1) require
 the use of Universal Time and 2) not require a definition of Universal
 Time that is tied to the rotating Earth?

*sigh*

LCT is currently tied to UTC, and converting a count of SI seconds to
a UTC time is currently (a) annoying and (b) depends on updating tables.

 Attempting to move the entire worldwide civil time system to a
 non-Earth based clock is equivalent to attempting to build a clock
 designed to run untended for 600 years - in effect, to attempting to
 build a millennium clock.  The alarm must be designed to ring in 599
 years time.

This is simply not true.  The LCT-TI offsets can be adjusted locally as and
when they individually start to be a problem.  No global changeover is required.

 Systems that don't need time-of-day should use TAI.

Wall clocks need to run in LCT, which is currently founded on UTC.  Most people
don't need precision time-of-day (which should be rightly called Earth angle
and measured in SI radians).  They just need there to be a rough correlation
between LCT and the sun, and several hours' discrepancy can be tolerated.
Just go to Urumqi, or Detroit if Urumqi is too remote.

 And most definitely, let's stop these inane and embarrassing closed
 door discussions among biased insiders.

Personally, I am a biased outsider.

 It ain't your clock - it's *our* clock.

Eh?  Who are you and who are we?

--
Not to perambulate John Cowan [EMAIL PROTECTED]
the corridors  http://www.reutershealth.com
during the hours of repose http://www.ccil.org/~cowan
in the boots of ascension.   --Sign in Austrian ski-resort hotel


Re: two world clocks

2005-01-20 Thread John Cowan
Rob Seaman scripsit:

 b) Currently the tables are maintained and updated by members of the
 precision timing community who should indeed be commended for their
 excellent work over the last quarter century and more.  The proposal on
 the table would require all 6+ billion of us to keep his or her own
 tables up-to-date.  The current situation is better.

I don't understand that at all.  People who need Earth angle (and I am
*not* opposed to making that widely available) will need to pick up
a correction table from IERS, there's no doubt about that.  IERS will
continue in exactly its current mission, it's just that its output
will no longer affect the value of LCT.

And as for keeping tables up to date, that's exactly what programmers
(especially programmers of embedded systems) are complaining about having
to do now, just to track UTC and LCT.

 People need good sources of time for a
 variety of reasons.  We are discussing a complete abandonment of the
 provision of Earth rotation information to the civilian public
 worldwide.

Not at all.  We are simply abandoning the notion that LCT is the right
way to provide that information.

--
Henry S. Thompson said, / Syntactic, structural,   John Cowan
Value constraints we / Express on the fly. [EMAIL PROTECTED]
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Obvious solutions

2003-08-19 Thread John Cowan
Markus Kuhn scripsit:

 Which reminds me of the obvious set of solutions to the problem that
 nobody at Torino even dared to mention:

I propagated this message to another mailing list, and received this reply:

 Nah. You don't have to get that drastic.  Studies have shown that
 fresh-water reservoirs affect the earth's spin.  Want to slow it down?
 Pump more water uphill!  Speed it up?  Move the water to Death Valley!
 It's only water.  It's only desert.  Who could complain! ;-)

Pumped-storage facilities could serve as pilot plants for this effort.

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Re: religious concerns

2003-07-14 Thread John Cowan
Markus Kuhn scripsit:

  http://www.sabbatarian.com/Dateline.html

 It seems, the true quarrel of this particular community is more with the
 Earth not being flat any more (as it obviously was when the Old
 Testament was written) ...

That seems to me by no means a sound criticism.  Given the writer of
the above page's relative values, it is indeed sensible for him to urge
that the International Date Line be moved to the meridian of Jerusalem,
and there are no arguments against this except sheer convention.

He does not appear to quite recognize that the IDL is a product of local
decisions rather than international agreement, but this is excusable.
He gets the more fundamental points correct:  the existing IDL is purely
conventional, the historical Sabbath is Saturday, the earth is round
and rotates.

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Re: Unix notion of Seconds since the Epoch

2003-01-30 Thread John Cowan
Markus Kuhn scripsit:

 It also provides the formula that defines the encoding of UTC into that
 integer, leaving no doubt about the exact semantics.

I agree that this is clear, and I continue to believe that it is a regrettable
and unjustified change from existing older practice, not a mere clarification
of it.

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May the hair on your toes never fall out! John Cowan
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Re: Leap-seconds, the epsilon perspective

2003-01-29 Thread John Cowan
Steve Allen scripsit:

 Which is more important...
 for civil time to be counted in SI seconds?
 for civil time to track the rotation of earth smoothly?

IMHO the former.

 Mark's alternative resembles the civil time solution adopted by the
 martian colonists in Kim Stanley Robinson's Red/Green/Blue Mars
 trilogy, where the clocks tick SI seconds, but every day at midnight
 they stop for 39.5 minutes of slip time to let the planet catch up.

I always thought that was silly.  How do you keep experiments running
(not necessarily precision-time ones, just ordinary ones) while your
clock is saying midnight, midnight, midnight, midnight,   And
what about Martian time zones?

 If we have decided that SI seconds are to be used,
 which is more important...
 for civil time to keep noon from drifting?
 for civil time to increase constantly?

The later.  Non-monotonic civil time would be a disaster, and we are
very lucky in the current regime that rotation is slowing and not
speeding up.

 Partly because eventually the scheme of turning UTC into a constant
 offset form of TAI requires a leap hour lest our descendants find
 themselves having their midday meal at 18:00 local civil time.  This
 sort of pushing the problem off onto our descendants implies that we
 really don't have the right solution, just one that salves some needs
 now.

I think it's utopian to suppose that a right solution exists; we are
trying to reconcile the fundamentally irreconcilable.  Eventually (a
very long time from now) we *will* have to abandon the 86400 seconds = 1 day
assumption.  (I utterly reject any attempt to redefine the SI second.)

 I suspect this would account for 99.9% of the world's clocks,
 including the clocks inside most computers, VCRs and microwave
 ovens; on your wrist; or next to your bed.
 
  Hmm.  How reasonable is it to expect this to change in future?

 If the future is a world of ubiquitous networking where Bill Gates can
 make every wristwatch and refrigerator magnet into a .NET client, then
 we should very much expect this to change.

Not what I meant.  I meant, how reasonable is it to expect to find 10^-8
reliable clocks in ordinary hands in the future?  If every clock is
indeed networked (a very unlikely future, I'd say), then of course the
time scale can be arbitrarily futzed with and all clocks will stay in sync.

--
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Re: What problems do leap seconds *really* create?

2003-01-29 Thread John Cowan
William Thompson scripsit:

 Any application which seeks to calculate the difference in time between
 two events recorded in UTC time needs to know if there are any leap
 seconds between the start and stop time.  For example, suppose you
 were studying solar flares, and analyzing some data taken in 1998,
 and you saw a burst of hard X-rays at 23:59:53 UT on Dec 31, followed
 by a rise in EUV emission at 00:00:10 UT the next day.  You'd think
 that the delay time between the two would be 17 seconds, but it's
 really 18 seconds because of the leap second introduced that day.

Thanks for the example.  Of course it is not astronomy-specific: the same
thing applies if you are calculating how long somebody spoke for in
field linguistics, or the amount of time it takes a moving part to stop
moving in engineering.  What we are dealing with here is time-zone independent
civil time.

 That's a vital difference for the scientific analysis of the data.

Indeed.

 And yes, part of that software package includes a list of all
 leapseconds added since 1 Jan 1972.  Currently, my software doesn't
 handle TAI/UTC conversions between 1958 and 1972, when UTC seconds
 had varying lengths.

Modern Unix time packages (both GNU and ADO) assume that TAI-UTC was 10
from the epoch until 1972-06-30T23:59:60 UTC.  Or to put it another way,
the epoch was at 1970-01-01T00:00:10 TAI.

When did the TAI timescale first come into existence?  One answer
seems to be that TAI was born on 1958-01-01T00:00:00 UT2, which was
also 1958-01-01T00:00:00 TAI.  But OTOH the definition of the SI second
changed in 1967 and again in 1997.  What did these changes do to the
uniformity of TAI?

I found the following interesting statement at
http://www.maa.mhn.de/Scholar/times.html :

#  The need for leap seconds is not caused by the secular slowdown
# of Earth's rotation (which is less than 2 milliseconds per century)
# but by irregular variations in this rotation and by the fact that the
# definition of the SI-second is fixed on the duration of the year 1900
# which was shorter than average.

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Re: what should a time standard encompass?

2003-01-28 Thread John Cowan
 and UT1 after only a few years.

Bully.  They might learn something about timekeeping thereby.

 To sum up:  the proponents of the notion of abandoning leap seconds
 have some obscure agenda of their own.

What's obscure about it?  No secrets here.  Forcing civil time to track
the earth's rotation, when 1200 LCT can see the sun halfway up or down the
sky, is overkill and a pain to keep track of.  And the list of leap seconds
only gets longer and longer, and fewer and fewer systems possess a fully
up-to-date list.

 This change to the standard
 is a sop to lazy projects who either can't be bothered to use UTC
 correctly - or shouldn't be using UTC at all, but rather, TAI or a
 related timescale like GPS.

I agree.  But when LCT is relevant, as is it is 99% of the time, *even to
astronomers* as members of the world community, then why shouldn't it be
straightforward to track it?

 In any event, many of these projects will
 have died a natural death before any change to the UTC standard could
 become a reality.

Civilian timekeeping will not go away.  The rotation of the Earth is a lousy
clock, as has been known since before atomic clocks were heard of, when the
standard for the SI second was a fraction of the tropical year.

As I have said before, it was once thought essential that the civil month
track the synodic month, and for some calendars it still does (Hebrew,
Muslim, Chinese are the ones I know about still in active use).  But somehow
we learned to deal with the autonomous civil month, even if it meant that
we couldn't tell the day of the month from the phase of the moon or vice versa
any more.  So too we learned to deal with the notion that apparent noon isn't
when the clocks strike twelve.  The precession of the equinoxes even entered
popular culture (to some extent) forty years ago, with the dawning of the
Age of Aquarius.  Can't we cope with this secular shift as well, in the
interest of simplicity for all non-astronomical applications?

--
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John Cowan [EMAIL PROTECTED]
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Re: Leap-seconds, the epsilon perspective

2003-01-28 Thread John Cowan
Dr. Mark Calabretta scripsit:

 Much of the problem boils down to the question of why we would want
 to continue to pretend that a mean solar day has exactly 86400 SI
 seconds when in fact, it has 86400+epsilon SI seconds.

I at least care that a *civil* day be 86400 SI seconds in length.
Mean solar days don't affect me to speak of.

 This suggests that, in order to eliminate leap-seconds, we should
 quit pretending that a mean solar day has exactly 86400 SI seconds
 and instead construct our clocks so that they measure its true length.

What for?  Why should we (the people of the Earth) care about mean
solar days?  For some purposes, apparent solar time is important, but
most of the time it's civil time that counts.  Why should that be tied
to mean solar days?

1) Any clock which keeps time to an accuracy of less than a few
   millisec per day (a few parts in 10^8) would not need changing.

   I suspect this would account for 99.9% of the world's clocks,
   including the clocks inside most computers, VCRs and microwave
   ovens; on your wrist; or next to your bed.

Hmm.  How reasonable is it to expect this to change in future?

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Re: what should a time standard encompass?

2003-01-27 Thread John Cowan
William Thompson scripsit:

  Because as a practical matter time-distribution protocols will never reach
  everybody, when you consider all the civil-time clocks in the world.
  Yet such clocks will be set, as a practical matter, from civil time.  This
  leads to a very segmented time indeed.

 From my point of view, this seems to be an argument against changing the system,
 rather than the reverse.  The argument of some people seems to be that
 astronomy's problems are irrelevant, and they should just depend on distributed
 time signals to make up the lack.

Currently *everyone* (not just astronomers) has to depend on distributed
leap-second information to just know what the local civil time is.  That is
a most unreasonable burden.

We can't do anything about the summer-time part of it, because that depends
on local political entities that can change their minds freely, but we
can do something about the leap seconds, viz. stop tying civil time to them.
The discrepancy between LCT and LMT is already in the multi-hour range
for some locations, and a half-hour or even an hour difference is considered
entirely normal.

 However, my point was that the burden will
 come down hardest on the much larger number of amateur astronomers and
 astronavigationalists who wouldn't necessarily have ready access to time signals
 for the ever increasing discrepency between a TAI-like time, and Earth rotation.

Compared to all the civil-time clocks in the world, the number of amateur
astronomers and astronavigationalists (nice word!) is small indeed, and
suitable low-bandwidth and high S/N communication channels already exist
for them.

 I find the argument that astronomer's objections are inconvenient, and thus
 should be just ignored, to be completely specious.

I don't care how many timescales astronomers set up for their special purposes,
and I encourage them to have lots of 'em, just as needed.

What I object to is tying the world's civil times to the rotation of the
Earth: civil days should always consist of 24 h of 60 m of 60 SI seconds each.

I also care, as a practical matter, that the name UTC, which is used
in (almost all of) the world's civil time legislation, be kept for that
purpose.  Astronomers can very well switch to a different abbreviation for
their |UTC - UT1|  0.9 timescale.

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