Re: Introduction of long term scheduling

2007-01-11 Thread Clive D.W. Feather
Rob Seaman said:
 Feather's encoding is a type of compression.  GZIP won't buy you
 anything extra.

Actually, it might with longer tables. For example, LZW (as used by Unix
compress) can be further compressed using a Huffman-based compressor.

 I'll join the rising chorus that thinks it need
 not appear in every packet.

Phew.

 I'd also modify Feather encoding to delta backwards from the
 expiration time stamp.

Interesting idea.

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Re: Introduction of long term scheduling

2007-01-08 Thread Clive D.W. Feather
Rob Seaman said:
 Which raises the question of how concisely one can express a leap
 second table.

Firstly, I agree with Steve when he asks why bother?. You're solving the
wrong problem.

However, having said that:

 So, let's see - assume:
1) all 20th century leap seconds can be statically linked
2) start counting months at 2000-01-31
 We're seeing about 7 leapseconds per decade on average, round up to
 10 to allow for a few decades worth of quadratic acceleration (less
 important for the next couple of centuries than geophysical noise).
 So 100 short integers should suffice for the next century and a
 kilobyte likely for the next 500 years.  Add one short for the
 expiration date, and a zero short word for an end of record stopper
 and distribute it as a variable length record - quite terse for the
 next few decades.  The current table would be six bytes (suggest
 network byte order):

0042 003C 

That's far too verbose a format.

Firstly, once you've seen the value 003C, you know all subsequent values
will be greater. So why not delta encode them (i.e. each entry is the
number of months since the previous leap second)? If you assume that leap
seconds will be no more than 255 months apart, then you only need one byte
per leap second. But you don't even need that assumption: a value of 255
can mean 255 months without a leap second (I'm assuming we're reserving 0
for end-of-list).

But we can do better. At present leap seconds come at 6 month boundaries.
So let's encode using 4 bit codons:

* Start with the unit size being 6 months.
* A codon of 1 to 15 means the next leap second is N units after the
  previous one.
* A codon of 0 is followed by a second codon:
  - 1, 3, 6, or 12 sets the unit size;
  - 0 means the next item is the expiry date, after which the list ends
  (this assumes the expiry is after the last leap second; I wasn't
  clear if you expect that always to be the case);
  - 15 means 15 units without a leap second;
  - other values are reserved for future expansion.

So the present table is A001. Two bytes instead of six.

If we used 1980 as the base instead of 2000, the table would be:

3224 5423 2233 3E00 1x

where the last byte can have any value for the last 4 bits.

I'm sure that some real thought could compress the data even more; based on
leap second history, 3 byte codons would probably be better than 4.

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Re: Mechanism to provide tai-utc.dat locally

2006-12-27 Thread Clive D.W. Feather
M. Warner Losh said:
 time_t is so totally broken, it isn't funny.  That's the closest thing
 to a standardized API there is for time.  All others are stuff folks
 have done here or there, but they aren't universal enough to be
 considered.

 Too bad the problems with time_t are well known, well discussed and
 well enumerated.  Or rather I should say too bad POSIX doesn't care
 enough to change it since the cost of changing time_t is huge...

Not so.

POSIX in the past deferred to WG14 (the ISO C committee) because that's
where time_t came from.

WG14 is willing in principle to make changes to time_t, up to and including
completely replacing it by something else. *BUT* it needs a complete and
consistent proposal and, preferably, experience with it.

Any proposal has got to deal with a whole load of issues, many of which
haven't been properly documented. For example, it should be possible to add
and subtract times and intervals (e.g. what time is 14 months and 87 days
from now?).

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Re: Titan Time

2006-10-26 Thread Clive D.W. Feather
Zefram said:
 There's nothing at all wrong with the radian - but there is a reason
 calculators let you switch between degrees and radians.  Each is best
 for particular purposes,
 Certainly the radian is best for some purposes.  But the degree?  Is there
 some inherent feature of the circle that makes it particularly natural to
 divide it into 360 parts?

Not really.

Personally, I like the mil: 6400 mils in a circle, and a mil is close
enough to a milliradian that you can use the usual tricks (a mil subtends
about a metre at a kilometre).

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Re: the case for created time

2006-07-19 Thread Clive D.W. Feather
Rob Seaman said:
 We have all been so utterly wrong!  The scales drop
 from my eyes (http://www.creation-answers.com):

 A theory of evolution for the creation of the solar system
 seems less than satisfactory in regard that the Earth and
 Moon appear to generate interrelated time cycles.

 A prize (well, a beer when next we meet) to the best
 explanation of what the heck this guy is on about...

He's another numerologist, finding patterns and coincidences in numbers
(something that will always appear if you keep looking) and trying to
claim they are significant.

For example, if you look at:
http://www.creation-answers.com/system.htm
he finds great interest in the fact that 50 years is approximately
(50*7*7 + 7)/4 lunar months [1], tying this into biblical rules about a
7*7+1 economic cycle. Similarly, 49 lunar months are almost exactly 1447
days.

From these coincidences he assumes that the system must have been designed
and created. He then assumes that the slight differences are proof of a
golden past when the numbers were exact. Typical creationist reverse logic.

[1] Except it's not - he's about 4 lunar months out, which he fudges
through a triennial leap week.

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Re: building consensus

2006-06-08 Thread Clive D.W. Feather
Rob Seaman said:
 In the UK in 1750, there were two different Julian calendars in
 use: the
 day and month enumeration matched, but year numbers changed at
 different
 dates (1st January in Scotland, 25th March in England and Wales).

 I've heard this said, but what exactly does this mean from the point
 of view of the people of the time?  Could see how the 1st of any
 month would be as good as any other for marking the count of years.
 But presumably you are saying something like that the sequence of
 dates was:

22 March 1750
23 March 1750
24 March 1750
25 March 1751
26 March 1751
27 March 1751

 Right?

Correct.

To quote *current* UK law:


That in and throughout all his Majesty's Dominions and Countries in Europe,
Asia, Africa, and America, belonging or subject to the Crown of Great
Britain, the said Supputation, according to which the Year of our Lord
beginneth on the 25th Day of March, shall not be made use of from and after
the last Day of December 1751;

and that the first Day of January next following the said last Day of
December shall be reckoned, taken, deemed and accounted to be the first Day
of the Year of our Lord 1752;

and the first Day of January, which shall happen next after the said first
Day of January 1752, shall be reckoned, taken, deemed and accounted to be
the first Day of the Year of our Lord 1753;

and so on, from Time to Time, the first Day of January in every Year, which
shall happen in Time to come, shall be reckoned, taken, deemed and
accounted to be the first Day of the Year;

and that each new Year shall accordingly commence, and begin to be
reckoned, from the first Day of every such Month of January next preceding
the 25th Day of March, on which such Year would, according to the present
Supputation, have begun or commenced:


 What this suggests to me is that the day-of-the-month and year-of-our-
 Lord counts were considered to be separate entities by folks of that
 time.

Right.

 Was also thinking to comment that day-of-the-week seems to have been
 considered quite distinct from day-of-the-month.  Our current usage
 is to tie all three together into a single unitary calendar.
 Presumably this dates from Gregory, too, along with all the other
 cycles his priests were seeking to synchronize.

No, this seems to be *much* older, coming from Jewish practice. Gregory
didn't touch the sequence of days of the week.

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Re: building consensus

2006-06-08 Thread Clive D.W. Feather
Zefram said:
 Looks a lot like that.  They used not to be, though: it seems that the
 oldest convention was to start the counted year on January 1, where Julius
 had put (well, left) the start of the calendar year.

Um, March was the first month of the year; look at the derivation of
September, for example. It seems that it moved to January in 153 B.C.
Wikipedia suggests it was 15th March before that (because the consuls took
office on the Ides of March).

 Counting the year
 from a different point is a distinctly mediaeval practice.

See above.

 Yes.  The seven day week is effectively a small calendar unto itself, and
 one much older than any of the year-based calendars we've been discussing.
 The Julian calendar was developed for a society that didn't use the week
 at all.  The week was adopted by the Roman Empire centuries later, as
 part of its Christianisation.

The *seven* day week was, but before then the Romans had a rigid *eight*
day week.

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Re: building consensus

2006-06-08 Thread Clive D.W. Feather
Poul-Henning Kamp said:
22 March 1750
23 March 1750
24 March 1750
25 March 1751
26 March 1751
27 March 1751

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

The 25th March is one of the four Quarter Days in England, when
traditionally quarterly rents were paid. In Scotland 1st January is a
Quarter Day.

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Re: building consensus

2006-06-08 Thread Clive D.W. Feather
Ed Davies said:
 Yes, I think that's right.  And, as I understand it, we still keep
 that change of year in mid-month but now it's on April 5th for the
 change of tax year.  When we switched from the Julian to the Gregorian
 calendar the tax year was kept the same length so its date changed.

That was another requirement of the legislation:


Provided also, and it is hereby further declared and enacted,

That nothing in this present Act contained shall extend, or be construed to
extend, to accelerate or anticipate the Time of Payment of any Rent or
Rents, Annuity or Annuities, or Sum or Sums of Money whatsoever, which
shall become payable by Virtue or in Consequence of any Custom, Usage,
Lease, Deed, Writing, Bond, Note, Contract or other Agreement whatsoever,
now subsisting, or which shall be made, signed, sealed or entred into, at
any Time before the said 14th Day of September, or which shall become
payable by virtue of any Act or Acts of Parliament now in Force, or which
shall be made before the Said 14th Day of September, or the Time of doing
any Matter or Thing directed or required by any such Act or Acts of
Parliament to be done in relation thereto;

or to accelerate the Payment of, or increase the Interest of, any such Sum
of Money which shall become payable as aforesaid;

or to accelerate the Time of the Delivery of any Goods, Chattles, Wares,
Merchandize or other Things whatsoever;

or the Time of the Commencement, Expiration or Determination of any Lease
or Demise of any Lands, Tenements or Hereditaments, or of any other
Contract or Agreement whatsoever; or of the accepting, surrendering or
delivering up the Possession of any such Lands, Tenements or Hereditaments;
or the Commencement, Expiration or Determination of any Annuity or Rent; or
of any Grant for any Term of Years, of what Nature or Kind soever, by
Virtue or in Consequence of any such Deed, Writing, Contract or Agreement;

[...]

but that

all and every such Rent and Rents, Annuity and Annuities, Sum and Sums of
Money, and the Interest thereof, shall remain and continue to be due and
payable;

and the Delivery of such Goods and Chattles, Wares and Merchandize, shall
be made;

and the said Leases and Demises of all such Lands, Tenements and
Hereditaments, and the said Contracts and Agreements, shall be deemed to
commence, expire and determine;

and the said Lands, Tenements and Hereditaments shall be accepted,
surrendered and delivered up;

and the said Rents and Annuities, and Grants for any Term of Years, shall
commence, cease and determine,
at and upon the same respective natural Days and Times, as the same should
and ought to have been payable or made, or would have happened, in case
this Act had not been made;

and that no further or other Sum shall be paid or payable for the Interest
of any Sum of Money whatsoever, than such Interest shall amount unto, for
the true Number of natural Days for which the principal Sum bearing such
Interest shall continue due and unpaid;


In other words, all financial matters are to be done by day count and not
by calendar date.

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Re: building consensus

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

No, I think it's just that my memory has converted 24.7 into 27.

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Re: building consensus

2006-06-08 Thread Clive D.W. Feather
Rob Seaman said:
 I thought Julius renamed some high value summer month and wanna-be
 Augustus did likewise, stealing a day from February to make August
 the same length.  If they put two extra months in, where were those
 62 days originally?

Very briefly:

- Julius and Augustus renamed months 5 and 6 respectively;
- Augustus moved one day from February to August as you say;
- the extra months (January and February) were inserted by Numa in the
  8th century BCE; until then there were no names for winter dates;
- until Julius's reforms, there was an intercalary *month* rather than day,
  inserted (I think) after February;
- Julius created a single 15 month year as a one-off adjustment to bring
  calendar back in line with the sun.

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Re: building consensus

2006-06-08 Thread Clive D.W. Feather
Rob Seaman said:
 John Cowan wrote:
 In the cover story, it was used as a final
 defense against the Invaders and destroyed by them.  In the true
 story, it was destroyed because it constituted a hazard, but I
 forget exactly how.
 Thanks!  But not sure true story is the opposite of cover story,
 here :-)

 Both versions of the book are sitting in a box somewhere in the
 garage.

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?).

For example, the official story is that Diaspar was the centre of a human
interstellar empire, while the true story is that man was part of a
multi-species federation.

It's these two stories that differ in what happened to the moon.

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Re: building consensus

2006-06-07 Thread Clive D.W. Feather
Rob Seaman said:
 As I've said before, eventually the notion that the solar day contains
 24h of 60m of 60s will have to be abandoned.  It'll be awfully hard
 to maintain when an hour involves two human sleep-wake cycles,
 out in the limit when the Moon is fully tidally locked and 1 lunar
 month = 1 solar day = 47 current solar days, more or less.

 Just returned from a conference three hours to the east.  The
 existence of
 jet lag suggests significant evolutionary pressure locking human sleep
 cycles to the length of the day.

Actually, the evidence from experiments is that the natural sleep-wake
cycle is about 27 hours long, but force-locked to the day-night cycle (it's
easier to synchronise a longer free-running timer to a shorter external
signal than vice-versa). So humans will cope until the solar day is about
27 (present) hours long, after which we'll probably start to move to a
system of two sleep-wake cycles per day.

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Re: building consensus

2006-06-07 Thread Clive D.W. Feather
John Cowan said:
 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.

Even worse, Julian can have more than one meaning.

In the UK in 1750, there were two different Julian calendars in use: the
day and month enumeration matched, but year numbers changed at different
dates (1st January in Scotland, 25th March in England and Wales).

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Re: 24:00 versus 00:00

2006-02-16 Thread Clive D.W. Feather
Markus Kuhn said:
 Writing 24:00 to terminate a time interval at exactly midnight is
 pretty common practice and is even sanctioned by ISO 8601.

 See for example the railway timetable on

   http://en.wikipedia.org/wiki/24-hour_clock

 where trains arrive at 24:00 but depart at 00:00.

Usual UK railway practice is to use 00:00 throughout in timetables,
including internal ones.

However, London Underground does print 24:00 on a ticket issued at
midnight, and in fact continues up to 27:30 (such tickets count as being
issued on the previous day for validity purposes, and this helps to
reinforce it).

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Re: marketing the leap second

2006-02-03 Thread Clive D.W. Feather
Steve Allen said:
 Here's a nice news piece on the marketing of a leap second

 http://www.marketingsherpa.com/sample.cfm?contentID=3174

However:

| Last December 31st, just before the clocks struck midnight in France, an
| extra leap second was added to the year. Instead of going from 11:59:59pm
| to 12:00am, extremely precise clocks went to 11:59:60.

In France the leap second was at 00:59:60.

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Re: Risks of change to UTC

2006-01-23 Thread Clive D.W. Feather
M. Warner Losh said:
 1500 years ago, no one spoke English.  Chances are the people that
 deal with this problem in 1000 or 2000 years won't speak any language
 recognizable to anybody alive today.

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

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

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Re: the tail wags the dog

2006-01-23 Thread Clive D.W. Feather
Steve Allen said:
 The official time of the US for commerce and legal purposes is UTC(NIST).
 The official time of the US DOD is UTC(USNO).
 The official time of the Federal Republic of Germany is UTC(PTB).
 etc.

The official time of the UK is GMT.

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Re: Fixing POSIX time

2006-01-20 Thread Clive D.W. Feather
Neal McBurnett said:
 UT1:Flamsteads birthday ?
 Cute.  1646-08-19

O.S. or N.S.?

At least it wasn't January, which would have added a third option.

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Re: interoperability

2006-01-09 Thread Clive D.W. Feather
Rob Seaman said:
 The question of delivering wall
 clock time is a trivial elaboration on first delivering common
 international business time.  (I'm trying on different terminology
 than civil time until I hit one that sticks.)

I don't accept that the concept exists. The international business
community still works - as far as I can tell - on the equivalent of Hello
Fred, what time is it there?.

 The event of migrating a time
 zone is a discontinuity just as with a leap second or leap hour.

So what? We go through such discontinuities twice a year in most years.
Some places more often. Read the TZ list archives.

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

Something which isn't and hasn't been true in many places.

What time is sunrise in Tromso today?

What time was sunrise on 1994-12-31 in eastern Kiribati?

 If Denmark or Elbonia decides to use a timezone which is offset
 from stage one by 1h3m21s, then it still works,
 Again, what is it, precisely?

Life.

 (but people travelling abroad will probably vote differently in the
 next election)
 Exactly.  The pressures to maintain a common international vision of
 time will trump local variations.

That's not pressure to maintain a common international vision, but people
not wanting to fiddle with the minutes and seconds on their digital
watches.

 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.

 Let's see - how does this work?

Just the way that it does right now.

 Under the current standard, 3600 small steps
 would have bled away the pressure.  Under the ITU notion, a leap hour
 would be needed.  A leap hour means moving UTC backward one hour (to
 let TAI pull ahead).  As I've said before, under the daylight saving
 analogy this is only naively a fall back event, it would be better
 to explicitly add a 25th hour.  But let's continue through to the
 logical conclusion of implementing this via fall back events (or
 the equivalent time zone shifting).

Except that time zone shifting means you don't affect the UTC sequence.

 A fall back event means that the clock (local, standard,
 international, whatever clock you want) first traverses an hour - and
 then traverses it again.

Right.

At present, there's a meridian corresponding to UTC that starts at
Greenwich, drifts back and forth with secular changes in the earth's
rotation and, when it approaches Cutty Sark or the Dome suddenly jumps. The
proposal is simply to have this jump abolished, so that the UTC meridian
starts drifting around the earth.

 Um.  How does one redefine the length of the day without changing the
 length of the second?  Answer:  by changing the number of seconds in
 the day.  I won't belabor the difficulty of selling the idea of
 having different hours of different lengths.

You mean just like now?

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Re: interoperability

2006-01-09 Thread Clive D.W. Feather
Rob Seaman said:
 I have heard no response to my discussion of techniques for achieving
 synchronization - of the difference between naive fall back hours
 and 25 hour days.  But how in practice is it envisaged that a scheme
 for migrating time zones versus TAI would work, precisely?

In the short term, by modifying the UTC-LTC function by adding a secular
term to the periodic one. Thus at present the function in the UK is:

dayofyear in [Last Sunday in Mar .. Last Sunday in Oct] ? 3600 : 0.

This would change to:

(dayofyear in [Last Sunday in Mar .. Last Sunday in Oct] ? 3600 : 0) +
(year  2600 ? 0 : year  3100 ? 3600 : year  3500 ? 7200 : ...)

or whatever. Note that we already have similar levels of complexity in
dealing with the changing summer time dates, the British Standard Time
folly, BDST during the war, and so on.

Note also that the Olsen tz code handles all of this just fine.

 Note, for
 instance, that nothing short of redefining the second can avoid the
 quadratic acceleration between the stage one and stage two clocks.
 Time zones (and the prime meridian?) would race more-and-more rapidly
 around the globe.

At some point, probably around the time that we're seeing an hourly shift
every year, people are going to have to divorce second from day, or at
least re-negotiate the terms of engagement.

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Re: The real problem with leap seconds

2006-01-09 Thread Clive D.W. Feather
I wrote:
 Right now, the DTAI(TAI) function is the sum of a set of Kroneker delta
 functions.

Thanks to David for quietly pointing out that I meant Heaviside step
functions, not Kroneker delta functions.

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Re: The real problem with leap seconds

2006-01-09 Thread Clive D.W. Feather
Poul-Henning Kamp said:
 So the standards crew, POSIX, LSB or whoever would have to come up
 with a new data type for holding timestamps,

We already have one: struct tm.

 There is no doubt that from a humanistic point of view it would be
 better to educate all the programmers, but considering that I still
 suffer from web-forms that insist I enter a USA style phone number
 when I have entered Denmark as country, this is a far moure
 daunting task than it might appear.

Amen.

[I happen to have a US Social Security number, which allows me to confuse
some web pages back.]

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Re: civil time = solar time

2006-01-05 Thread Clive D.W. Feather
Rob Seaman said:
 Rather, the often repeated canard that civilians don't give a fig for
 the actual position of the sun in the sky implies that it is
 precisely apparent solar time that only queer ducks like astronomers
 care about.  Mean solar time is what civilians DO care about.

Only *very* *very* approximately.

In the UK, sunset varies from about 15:30 to about 22:30 LCT. Sunrise isn't
an event most people even care about (for me, it shifts from happens at
work to happens before I get up on an annual basis but, during the
winter, on a weekly basis as well).

Provided that astronomical noon is between about 08:00 and 16:00, most
people won't care.

For unless they see the sky,
But they can't, and that is why
They know not if it's dark outside or light.

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Re: Longer leap second notice

2006-01-05 Thread Clive D.W. Feather
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.

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Re: Lighter Evenings (Experiment) Bill [HL]

2005-12-19 Thread Clive D.W. Feather
Poul-Henning Kamp said:
 Not strictly on topic but probably of interest - a Bill in the UK House of
 Lords which I just came across when looking for something else:

 A Bill To
 Advance time by one hour throughout the year for an experimental period;
 and for connected purposes.

 the entire notion and I belive the welch are not too happy either.

Not if you call them that!

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Re: a system that fails spectacularly

2005-12-09 Thread Clive D.W. Feather
Steve Allen said:
 This became a long-running joke in the morris dance community.  A few
 years back some English town councils decided to become ISO 9000
 compliant.  That required them to ascertain that all of their
 sub-contractors were also compliant.

Actually, it does nothing of the sort.

An organisation going for qualification must set up an ISO 9000 boundary.
Everything inside must conform to the processes, so anything coming in
through the boundary must be assessed each time it comes in.

The boundary can go around more than one organisation. So many organisations
find it easier to force their suppliers and sub-contractors inside the
boundary than to deal with stuff coming in. In other words, it's easier to
only buy widgets from ISO 9000 compliant suppliers than to provide an
inbound widget quality test department.

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Re: a system that fails spectacularly

2005-12-09 Thread Clive D.W. Feather
M. Warner Losh said:
  * A second is represented by an integer from 0 to 61;
[...]
  but this specification
  follows the date and time conventions for ISO C.

Of course, ISO C fixed this misunderstanding many years ago.

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Re: BBC - Leap second talks are postponed

2005-11-17 Thread Clive D.W. Feather
John.Cowan said:
 GMT is, unfotunately, widely used to mean the time in Britain
 during winter.

 Indeed, it is sometimes used to mean that even in the summer.  There was
 some confusion in my company last year about a teleconference scheduled in
 GMT which turned out to actually refer to British Summer Time.

Microsoft *spit* Outlook calendar management talks about GMT Daylight
Savings Time or some such idiocy. Every spring I respond to the first
appointment request from my boss with so do you want to meet at 10:00 GMT
or 10:00 BST?.

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Re: vive le BIH!

2005-08-29 Thread Clive D.W. Feather
John.Cowan said:
 Another point made in the article, that GMT is a conventional name
 for the U.K.'s LCT, is all too true.

No, it isn't.

 Recently I was to take part in a
 teleconference scheduled for such and such a time GMT.  Since I live on
 a small island off the coast of North America, I am in UTC-4 currently,
 and I naively interpreted the time as UTC+0, but in fact UTC+1 (BST)
 was meant.  Oopsie.

The problem here is Microsoft, whose software appears to believe that the
current LCT here is GMT Daylight Time.

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Re: Consensus rather than compromise

2005-08-29 Thread Clive D.W. Feather
John.Cowan said:
 Rather, the very definition of
 civil time was misunderstood, whether by Microsoft or by somebody
 else.
 I think this greatly overstates the case.

Exactly.

 There was a mere misapplication
 of labels involved, both in the case of the conference leader (who believes
 that the name GMT refers to the LCT of the U.K.)

Which is a relatively rare belief, easily countered by (for example)
looking at the BBC news web site.

 and the anonymous Microsoft
 programmer (who believes that British Summer Time should be called
 GMT Daylight Time).

Exactly. The belief that the T means Time, therefore it's subject to DST.
I wonder if it mishandles zones near the equator which don't have DST?

Neither are to do with the *definition* of civil time [1], but with its
name.

[1] Microsoft has been known to get this wrong as well, attempting to apply
US rules to the EU.

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Re: Consensus rather than compromise

2005-08-29 Thread Clive D.W. Feather
Rob Seaman said:
 The problem here is Microsoft, whose software appears to believe
 that the current LCT here is GMT Daylight Time.

 The case has been repeatedly made that since the world tolerates
 large excursions in civil time such as caused by the varying local
 Daylight Saving Time policies,

and by these policies changing, sometimes on short notice, yes.

 that the world's institutions and
 populace will be able to simply ignore leap hours on those rare
 occasions when they are needed.  What is offered up is evidence for
 the exact opposite.

False.

 We're shown that Daylight Saving has been
 mishandled in a trivially simple instance and that the GMT standard,
 synonymous with UTC, is capable of misinterpretation (by minions of
 the richest man on Earth) completely distinct from leap second
 related issues.

No, it appears that a few people think that the GMT standard is
synonymous with UK local time. This is just as much a fallacy as the belief
that Indiana currently observes US Central Time.

And, by the way, the GMT standard is *NOT* synonymous with UTC; it is
(IIRC) UT1.

 Nothing about the ITU proposal would mitigate the
 situation being discussed.

True. Nor would it mitigate the Indiana problem.

Nor, incidentally, would it harm either.

 It would be the constant daily persistence of a large DUT1
 that would make leap hours unpalatable

Why?

Apart from astronomers, of course, who actually cares what the value of
DUT1 is? Consider the value DLCT (LCT-UTC). This varies between -1 and
3601 over the year, yet the only effect it has is that it varies whether or
not I have to turn on the car headlights on the way to work.

 And if
 civilians are surprised by the requirements of civil time now, how
 much more so they will be in a world in which the last leap hour
 troubled their great-great-...-great-grandparents?

Yet they cope with the complex proposals to move counties of Indiana
between zones, or to move DST end-dates every decade or so. We coped with
the introduction of British Standard Time and its abolition.

I suggest that fiddling with the hourly shifts will continue every few
years ad nauseam, so one more reason for doing so won't bother anyone.

 Contrast
 this with a well-formed consensus - several disagreeing factions are
 locked in a room until they all agree on a common vision of how to
 proceed.  Call this the Twelve Angry Men effect.  That one faction
 or another may have to completely change their original position is a
 strength, not a weakness.  Ideally none of the factions even arrives
 in the room with a specific position to bargain over, but rather
 arrives only with general requirements and objectives.

That works when it works. Not when there are irreconcilable differences in
the general requirements and objectives.

 What is needed is civil time to continue to reflect solar time as it
 has since literally the dawn of time.

Within a couple of hours plus or minus.

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Re: Precise time over time

2005-08-12 Thread Clive D.W. Feather
Poul-Henning Kamp said:
 As I said, 50 years seems right, and it does so because there is
 no currently running computer that has worked for 50 years.

Actually, the programme machines that control the signalling of much of
the London Underground are somewhat older than that. They run to, IIRC, a
15 second accuracy (I'd have to dig out various technical papers to be
sure).

 In the US I belive something is antique when it is 25 years old,
 in Europe I think it has to be 50 years old to gain the distinction.

100 years.

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Re: GMT - UTC in Australia

2005-02-25 Thread Clive D.W. Feather
Rob Seaman said:
 No reasonable standard can be based on constraining the behavior of our
 descendants 600 years hence.

In what way is the requirement |DUT| = 0.9s not constraining the
behaviour of our descendants 600 years hence?

While I understand your argument about the name UTC:
* *EVERY* approach requires constraining the behaviour of our descendants
  600 years hence, just in different ways;
* Universal Time is a *really* stupid name for a time scale based on
  the variable rotations of one small piece of rock.

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Re: our customers' needs

2005-01-27 Thread Clive D.W. Feather
Rob Seaman said:
 Our modern sensibility may lead us to discount Egyptian and Druidic (or
 earlier) world views, but surely the many cultures worldwide that
 produced pyramids and other monolithic structures do demonstrate the
 frequent centrality of spirituality in human decision making.  Those
 cultures most definitely knew the motions of the Sun, Moon, stars and
 planets intimately.  Steve Allen already provided a convincing real
 world example of the response of a more recent mainstream religious
 community to civil calendar issues.

This would be the point about sunrise on saints' days?

All these issues have one thing in common - they pre-date the introduction
of atomic time, but rather date back to when mean solar time was assumed to
be constant rate and therefore unchanging.

What, I wonder, did the various churches do about the Eleven Days? They can
hardly have been taken down and rebuilt at a slight angle, after all.

 At this critical point in world
 history, what possible justification could there be for truncating the
 discovery process for uncovering similar requirements placed on civil
 time by the great religions of the world before making a large change
 in the definition of civil time?

I have no problem with trying to identify the issues involved. But we can
reasonably ask whether the alignment of a few buildings in Oxfordshire [*]
is grounds for forcing the whole world to cope with the kludge of leap
seconds for the next thousand years.

[* Usual Cambridge-Oxford rivalry deleted for brevity.]

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Crustal rebound

2005-01-26 Thread Clive D.W. Feather
Markus Kuhn said:
 The US and UK are
 actually no different from that, except that the subtle differences
 between GMT and UTC have escaped political attention in these two
 countries so far, and as a result, they still have a technically rather
 vague definition of time in their law books,

Actually, UK law is clear that civil time is GMT/GMT+1.

Last night I found myself talking to a UK legislator on the matter of UTC
versus GMT. We got as far as the quadratic nature of the TAI-UT1
difference, and that it was smaller than expected because - according to my
reading - of crustal rebound following the last ice age.

At which point we were both confused about the physics involved. If the
crust is rebounding after being compressed by ice sheets, surely the
earth's moment of inertia will increase and the rotation should slow *more*
than otherwise expected. So can someone unconfuse us, please?

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Re: ITU Meeting last year

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

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

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

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

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

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

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

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Re: more media coverage

2003-07-22 Thread Clive D.W. Feather
Steve Allen said:
 CNN is broadcasting the video form of this story today

 http://www.cnn.com/2003/WORLD/europe/07/22/time.boulden/index.html

 I surmise that Mr. Catchpole was not prepared with the figures.

He also seems to be unaware of the legal status of GMT in the UK.

[Incidentally, if I recall correctly the building at Greenwich is now just
a museum, with the RGO having been abolished.]

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

2003-01-30 Thread Clive D.W. Feather
John Cowan said:
 Fact 2 is that the old 1980s pre-POSIX Unix manuals talked about GMT and
 not UTC. This strongly suggests that the authors were unfamiliar with
 both TAI and UTC. The seconds they refer to behave more like UT1
 seconds than like TAI/SI seconds, i.e. they are Earth rotation angles
 and not Caesium oscillations.
 Where do you see any reference in the old documentation to the rotation of
 the Earth?  The authors of those man pages were engineers, and they knew
 perfectly well what a second was and is (since 1967), and they certainly
 knew the difference between measuring/counting and encoding.

I was around, though on the margins, when the first POSIX standard was
being written. If there had been an awareness of the difference between UTC
and GMT, I am the sort of person who would have leaped on it in an attempt
to win a Weirdnix prize. I offer this as weak evidence in support of
Marcus - nobody was discussing stuff at this level of detail.

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