On Thu, 14 Jun 2007, Greg Hennessy wrote:
To codify existing practice. We don't use GMT any more, we use UTC. It isn't
even clear that with the closing of Greenwich observatory if GMT even exits.
GMT ceased to exist long before the RGO was dissolved as an organization.
The meridian marked on
On Mon, 24 Sep 2007, Barberi wrote:
Funny, I was just helping some kids with a project on the 1884 Washington
Conference. Various ideas for time zone systems were discussed, but no
recommendation was made.
Recommendations 9 - 12 describe the time zone system.
On Sat, 9 Feb 2008, Steve Allen wrote:
I think that POSIX time_t should be redefined to be TI, with no leap
seconds. I think that the leap seconds should be included in the
zoneinfo files. POSIX already allows that the local time can be
offset by an arbitrary number of seconds (not just
On Wed, 13 Feb 2008, Rob Seaman wrote:
The day is a key concept in our civilization. The mean solar day is
the natural way to implement this. Sundials have nothing to do with the
mean solar day, but rather the apparent solar day.
How does the mean solar day relate to ephemeris time? Between
On Fri, 28 Mar 2008, Steve Allen wrote:
Part of the beauty of distinguishing broadcast time signals from UTC,
while continuing both, is that it allows separate issues to be
addressed separately.
I allow that the broadcast time signals should be leap free, for there
are many operational
On Mon, 31 Mar 2008, Clive D.W. Feather wrote:
Um, what buttons on the back? My kitchen RC clock has none such (probably
because just about all of the UK is in the same time zone).
Mine has buttons to request a radio sync and for manual setting.
On Wed, 9 Apr 2008, Rob Seaman wrote:
Yeah, I saw that too, but haven't figured out what symbols he's talking about.
I just see the familiar text files. Anybody have specific links?
http://www.iers.org/MainDisp.csl?pid=36-1100218
The link is the small white square with the red diagonal line
On Mon, 15 Sep 2008, Rob Seaman wrote:
Hence the prevalence of radians in everyday use :-) The only thing natural
about the metric system is that humans have ten fingers and the quadrant of
the Earth something approximating 10 megameters.
The latter was an artificial and deliberate design
On Sun, 9 Nov 2008, Peter Bunclark wrote:
So a User requirement might be:
The rythms of life, including the orbits of the earth and the moon,
the rotation of the earth, and convenient sub-divisions of the rotation
down to nearly the limit of human perception, shall be expressed in
a single
On Wed, 12 Nov 2008, Rob Seaman wrote:
Clive D.W. Feather wrote:
No, it's because there are no applications where people need to say what
would my GPS receiver had said in 1751?. Whereas people do need to
represent older times in (say) POSIX time.
Do they? Example use case from 1751?
On Wed, 12 Nov 2008, Rob Seaman wrote:
Are people really convinced by the argument that badly implemented systems
should determine policy?
I'm arguing about deployment pragmatics. Note that the systems aren't
badly implemented, they are just following specs based on UT sans leap
seconds.
If
On Fri, 12 Dec 2008, Zefram wrote:
[ISO 8601 is] neutral about whether and when leap seconds may occur:
that's an application issue. The timezone designators are specifically
described as being relative to UTC, but it is more consistent with the
rest of the standard to treat that mention of
On Sun, 14 Dec 2008, Zefram wrote:
NOTE These expressions apply to both UTC and non-UTC based time
scales for time of day.
This seems to be the crucial bit that you missed. It's explicit about
allowing time scales other than UTC, and doesn't restrict the choice
of time scale
On Mon, 22 Dec 2008, Zefram wrote:
http://upload.wikimedia.org/wikipedia/commons/9/98/Orbit_times.png
Cool, thanks for that and the interesting details in your other post.
Tony.
--
f.anthony.n.finch d...@dotat.at http://dotat.at/
WIGHT PORTLAND PLYMOUTH: VARIABLE BACKING SOUTHEAST 3 OR 4,
On Mon, 22 Dec 2008, Steve Allen wrote:
I am aware of the interesting breakages that happened when zoneinfo
files were retroactively modified to be inconsistent with POSIX.
Clearly that change cannot be done for past history.
It can't be done for future history either, because it breaks
On Mon, 22 Dec 2008, Rob Seaman wrote:
The fact that the mean solar rate differs from the SI rate is the whole
enchilada. I have to put the Christmas lights on the tree, but you could
search leapsecs for secular and periodic to locate my screed on this
topic.
The mean length of year differs
On Tue, 23 Dec 2008, Zefram wrote:
Either of my scenarios still suffers from the problem that the TI-UT
difference accelerates. These timezone offset changes would be needed
at decreasing intervals. By the time timezones are jumping by an hour
every year, one might expect to see political
On Sat, 27 Dec 2008, Rob Seaman wrote:
Rather, a clock can be deposited at any meridian on any planet, set to any
time, running at any rate. The question is whether a particular choice of
parameters is useful and sustainable.
Really what it boils down to is a question of how frequently and
On Sat, 27 Dec 2008, M. Warner Losh wrote:
However, the die was cast on this in 1958 when the second was defined in
terms of atomic behavior. At that point, the game was up, since the
basic unit of time was decoupled from the day.
The decoupling occurred before then, when the second was
On Sun, 28 Dec 2008, David Malone wrote:
Broad agreement and consensus is the foundation of civil time. The way
that leap seconds work clearly does not have enough consensus, in that
people still produce software and standards and specifications that
are incompatible with leap seconds.
On Sun, 28 Dec 2008, Poul-Henning Kamp wrote:
In addition to the Olsen database, the book Calendrical Calculations
is probably required.
Calendrical Calculations isn't a reliable source for historians in the
way that the Olson database tries to be. CC is a mechanized description of
how
On Sun, 28 Dec 2008, Zefram wrote:
The numerical algorithms are correct, as far as I can see, but the
descriptions of the underlying theory are often muddled, riddled with
errors and critical omissions. (Count how many different quantities go
by the name RD.) Rather importantly for our
On Tue, 30 Dec 2008, M. Warner Losh wrote:
Time used to be strongly coupled to the earth.
Only because it was the most accurate clock we had. It might still be the
most reliable clock we have but our natural tendency to optimisation means
that isn't the most important consideration.
Actually,
The Guardian soeaks to Peter Whibberley, a senior research scientist at
the National Physical Laboratory. There's discussion about the future of
leap seconds, and he's against any change in line with the UK's national
policy as we saw in the WP7a summary.
On Thu, 1 Jan 2009, Rob Seaman wrote:
NTP is proof of concept that automation is possible once the schedule is
released.
Yes for high stratum clients, but the lowest stratum servers need their
leap second file kept up-to-date, which is a manual task that is often not
performed correctly.
On Wed, 31 Dec 2008, Daniel R. Tobias wrote:
On 31 Dec 2008 at 8:08, Poul-Henning Kamp wrote:
Notice the near: the 0° meridian no longe passes through the
transit instrument there.
They moved it? (The meridian, or the transit instrument?)
The meridian moved several times. About a year
On Fri, 2 Jan 2009, Rob Seaman wrote:
Mean solar time is highly regular and elegantly simple.
Compared to our clocks it's too irregular.
Civil timekeeping (even under the ITU proposal) is about the underlying
diurnal period.
What does atomic time have to do with the position of the Earth?
On Fri, 2 Jan 2009, Magnus Danielson wrote:
b...@po.cwru.edu skrev:
That's 303*365+97*366=146097 days for an average of 365.2425 days per year.
Your arthmetic describes solar days, but fails to describe the sidereal days.
No, he's talking about calendar years, as opposed to the
On Fri, 2 Jan 2009, Rob Seaman wrote:
So yes, I think the angular momentum of the Earth is more real than the
observations that might be compiled to generate an estimate for its value.
But the value is an estimate, so if you plug numbers into a model based on
this estimate you are only going
On Mon, 5 Jan 2009, Poul-Henning Kamp wrote:
The proper thing for the future is either a int128_t 64.64
fixedpoint time representation or a double ditto.
Do you mean double as in the C type? Which is surely too small - you want
quad-precision FP or perhaps double double (paired doubles to get
On Mon, 5 Jan 2009, Rob Seaman wrote:
The recent leap second passed (yet again) with no major issues.
Wrong.
Loads of Oracle RAC servers crashed because of a bug triggered by the
clock going backwards.
http://www.merit.edu/mail.archives/nanog/msg13857.html
Many time dissemination systems got
On Mon, 5 Jan 2009, Magnus Danielson wrote:
You could of course to some degree steer the clock on a machine by
changing the computing load on it, as the tempco of most systems crystal
is pretty bad. It would kinda work except when it is out of controlrange.
Alternatively you can use clock
On Mon, 5 Jan 2009, Rob Seaman wrote:
Is it too much to ask that an attempt be made to describe how the logistics
would work?
Exactly the same way that current time zones work. Every so often,
jurisdictions that become dissatisfied with their current timezone offset
or DST arrangements because
On Tue, 6 Jan 2009, Rob Seaman wrote:
Your April Fool's post on risks may be the most coherent analysis I've
read on the subject [of DST].
Thanks :-)
Where I grew up in the U.S. mid-Atlantic states, the most obvious effect of
DST was to extend the usable hours of daylight for Summer
On Tue, 6 Jan 2009, Rob Seaman wrote:
Tony Finch wrote:
This is why DST is a sensible solution to the problem of the mismatch
between natural human preferences and inflexible timetables based on mean
solar time.
I don't think inflexible is the right choice of words, but I'll let it pass
On Tue, 6 Jan 2009, Rob Seaman wrote:
To return to a previous point, Tony Finch wrote:
Note that there's no need for global co-ordination. Each country (or
county) can change when it is convenient for them. The effect would
probably be a shifting of timezone boundaries in lumps and bumps
On Mon, 5 Jan 2009, Rob Seaman wrote:
Alternately, by relying on shifting timezones, there would be no
underlying stabilized civil timescale permitting commonsense timekeeping
inferences by humans.
What do you mean by stabilized here? Atomic time is the basis of our
most stable time scales. I
On Wed, 7 Jan 2009, Rob Seaman wrote:
On the other hand, permitting a long delay between events - or rather,
between scheduling opportunities for events - risks losing the corporate
knowledge to handle the events properly.
The good thing about timezones is the code to implement them and alter
On Mon, 16 Feb 2009, Steve Allen wrote:
And that means that the POSIX epoch encompasses almost as much
proleptic fantasy as the use of UTC (or GMT) for the 1601 epoch. The
observatory at Greenwich wasn't commissioned for another 75 years, not
until after 3 coronations and a civil war. I
On Tue, 17 Feb 2009, Gerard Ashton wrote:
Concatenate the epoch time at the time this ID value is being
generated ; the epoch time is the number of seconds elapsed since
00:00:00 Coordinated Universal Time (UTC) January 01,
1970 (not counting leap seconds)
2. It has all the
On Tue, 17 Feb 2009, Joseph M Gwinn wrote:
The navigators who used marine chonometers knew perfectly well that
those chronometers did not keep the right time as measured by clocks
on land being reset by telescopes. Instead they knew that if their
chronmeters were treated well they kept
On Thu, 10 Sep 2009, Rob Seaman wrote:
It is precisely the fact of a international civil timescale that makes the
timezone system work.
Yes.
In return, the many timezones and numerous special cases represent
constraints on the common underlying standard to better track mean solar
time.
Is there a generic term for timescales like POSIX time_t and NTP that
count seconds (or some other interval) since an epoch without taking
leap seconds into account?
Tony.
--
f.anthony.n.finch d...@dotat.at http://dotat.at/
GERMAN BIGHT HUMBER: SOUTHWEST 5 TO 7. MODERATE OR ROUGH. SQUALLY
On Tue, 9 Mar 2010, Steve Allen wrote:
On Tue 2010-03-09T17:07:01 +, Tony Finch hath writ:
Is there a generic term for timescales like POSIX time_t and NTP that
count seconds (or some other interval) since an epoch without taking
leap seconds into account?
mean solar time
thus
On 11 Mar 2010, at 02:20, M. Warner Losh i...@bsdimp.com wrote:
But maybe we need to borrow from my college days in physics class
and call it an idealized time count or something like that to show
that it is a polite fiction that makes the math easier and mostly
right most of the time...
On Thu, 5 Aug 2010, Steve Allen wrote:
On Thu 2010-08-05T14:55:25 -0600, M. Warner Losh hath writ:
in the UK there's not a clear distinction between GMT and UTC and
often (but not always?) the terms are used interchangeably.
Listen to the BBC. Many of the readers will announce that it's
X
On Fri, 6 Aug 2010, Poul-Henning Kamp wrote:
For starters, the actual change happend in 1958 when the clock
running the free-of-charge Fr?kken Klokken telephone service
was adjusted to UTC.
Er, no. 1958 was when TAI started. The predecessor of UTC started in 1961.
(Which is not to disagree
On 12 Aug 2010, at 21:25, Michael Deckers michael.deck...@yahoo.com wrote:
I fear that the matter is less simple. The proposal keeps the
name UTC for the newly defined timescale. (And unfortunately,
there is precedent with essential changes in definitions of well
established time
On Wed, 1 Sep 2010, Daniel R. Tobias wrote:
If the time zone boundaries were drawn with any sort of logic with
respect to keeping the times close to the natural solar time in each
location, then France and Spain would join the UK and Portugal in
WET, rather than the UK shifting the other way.
On 3 Sep 2010, at 04:47, Daniel R. Tobias d...@tobias.name wrote:
So you'd like to end up with an even more chaotically convoluted time
zone map than we already have? Eventually, there'd have to be
offsets from UTC of 36 or 48 hours, way beyond the theoretical +12
and -12 (already
On 3 Sep 2010, at 05:50, Rob Seaman sea...@noao.edu wrote:
I was referring to GMT broadly as the astronomical timescale and for all
practical purposes de facto the same as UTC.
My point is that if you are being precise this is nonsense. GMT in the historic
sense of a solar timescale does not
On Fri, 3 Sep 2010, Zefram wrote:
Tony Finch wrote:
Thanks for the informative explanation, but GMT is not and was not UT1.
Picky, picky. OK, let's look at the strictest sense of GMT, taking the
Greenwich meridian to be defined by the Royal Observatory, Greenwich,
rather than by the ITRF
On Fri, 3 Sep 2010, Zefram wrote:
Tony Finch wrote:
As we have seen there are a lot of intricate
details whose necessity people can legitimately disagree about and no way
to determine an official consensus. Which is why I say that astronomical
GMT doesn't exist
On 3 Sep 2010, at 22:14, Rob Seaman sea...@noao.edu wrote:
Greenwich Mean Time is the Mean Solar Time in Greenwich. Is this its
historical astronomical meaning? Or is this its definition?
The former, because in current usage it is a synonym for UTC (which I do not
regard as an astronomical
On 3 Sep 2010, at 21:02, Nero Imhard n...@pipe.nl wrote:
But indeed DST has its own costly problems. The burden of moving all clocks
twice a year, made worse because every microwave and refrigerator comes with
its own clock these days (none of which are self-setting of course), falls on
On Mon, 6 Sep 2010, Poul-Henning Kamp wrote:
There was a lot of noise in EU context, and that resulted in one of the
technical requirements for EU membership being that countries do not
f**k with their summertime, and presumably timezones, with anything less
than 5 years notice.
Interesting.
On Mon, 20 Sep 2010, Robert Seaman wrote:
To say that leap seconds were devised to keep the UTC time scale in
close alignment with earth time making UTC useful for celestial
navigation is to suggest two unsupported assertions. First that no
other requirements for earth time exist, and second
On 22 Oct 2010, at 18:16, Rob Seaman sea...@noao.edu wrote:
On Oct 22, 2010, at 9:43 AM, Matsakis, Demetrios wrote:
I have now heard from two sources that the revised ITU-R draft
recommendation TF.460-6 passed a major hurdle in Geneva last week. It will
be sent by SG7 to the January 2012
On Tue, 2 Nov 2010, Poul-Henning Kamp wrote:
Finagle Subject to
FactorUnit/Resolution politics since
Leap days 86400 sec. 2000 bc.
Timezones 3600
On Tue, 2 Nov 2010, Poul-Henning Kamp wrote:
I may be misremembering, I thought the longitude conference was in 1884 ?
Yes, but by that time there had already been 40 years of railway time in
the UK. We officially switched to a single time zone in 1880, but local
mean solar time had already
On 2 Nov 2010, at 20:38, Poul-Henning Kamp p...@phk.freebsd.dk wrote:
In message 20101102202753.gc21...@ucolick.org, Steve Allen writes:
Section A.4.15
http://www.opengroup.org/onlinepubs/9699919799/xrat/V4_xbd_chap04.html
Note that as a practical consequence of this, the length of a
On Tue, 2 Nov 2010, Poul-Henning Kamp wrote:
Tony Finch wrote:
On Tue, 2 Nov 2010, Poul-Henning Kamp wrote:
I may be misremembering, I thought the longitude conference was in 1884 ?
Yes, but by that time there had already been 40 years of railway time in
the UK. We officially switched
On 19 Dec 2010, at 01:18, Magnus Danielson mag...@rubidium.dyndns.org wrote:
This is true, if we by computing means POSIX.
There are many standards other than POSIX which use a POSIX timescale or one
equivalent to it. For example, NTFS, DNSSEC and NTP's basic timescale.
POSIX as extended by
On 23 Dec 2010, at 07:48, Poul-Henning Kamp p...@phk.freebsd.dk wrote:
In message 66237b3a-3953-43ff-86d6-9ae1befa5...@tcs.wap.org, Jonathan E.
Har
dis writes:
You might want to rephrase that as a trivia question: WHERE under
U.S. jurisdiction is UTC (no offset) the legal, civil
On 24 Dec 2010, at 14:29, Ian Batten i...@batten.eu.org wrote:
UTC is not _legal_ time in the UK, as Clive points out.
De jure perhaps, even though GMT as such no longer exists since funding to
maintain it was withdrawn decades ago. Nowadays GMT is for UK civil time
purposes a de facto
On 24 Dec 2010, at 23:54, Ian Batten i...@batten.eu.org wrote:
I'm not sure what you mean by Greenwich NTP servers.
They are actually across the river in Telehouse. They were part of a millennial
government / industry marketing effort to promote the use of NTP on home
computers.
On 25 Dec 2010, at 17:07, Ian Batten i...@batten.eu.org wrote:
Which is sort-of the point: that whatever the UK government's tactical
movement around GMT, UTC or whatever might be, it isn't long-term, it isn't
serious and it isn't in any way indicative of long-term policy.
It isn't serious
On 28 Dec 2010, at 16:27, Michael Deckers michael.deck...@yahoo.com wrote:
[b] This proposal does not only change technicalities like
the maximal difference |UTC - UT|, but it changes several
other things (more important things, in my opinion). For
instance, it removes
On 31 Dec 2010, at 02:39, Rob Seaman sea...@noao.edu wrote:
Rather, closed shop organizations like the ITU should embrace open discourse
themselves.
AIUI the ITU-T is rather more open than the ITU-R: for example, ITU-T specs are
published online for free (unless they are joint ISO specs).
On 1 Jan 2011, at 18:06, Rob Seaman sea...@noao.edu wrote:
On Jan 1, 2011, at 10:38 AM, Tony Finch wrote:
Actually, based on Steve Allen's table it looks like using time zone
adjustments to keep civil time in sync will work for thousands of years.
We'll probably hit the Y10K problem before
On Fri, 7 Jan 2011, Rob Seaman wrote:
It is a requirement - a description of the problem space - that manifold
human activities are loosely or tightly coupled to the synodic day.
Which? UTC with leap seconds is tightly coupled to the day. Atomic time
adjusted with a locally-determined timezone
On Fri, 7 Jan 2011, Warner Losh wrote:
Eliminating leap seconds keeps the period of the day constant.
Not really, because there is no single period of the day :-) There are
days according to UT1, UTC, local time, etc. and these lengths all differ
and none of them is (currently) constant. Fixing
On 7 Jan 2011, at 20:53, Rob Seaman sea...@noao.edu wrote:
The proposal as written asserts that humans don't care about the synodic
length of day.
No, it says 86400 SI seconds is close enough for civil time. The aim is to
reduce the need for synchronization adjustments - eliminate frequent
On Sat, 8 Jan 2011, Rob Seaman wrote:
I do not believe the unstated magic timezone notion (if indeed that is
an idea motivating the authors of the draft in front of the ITU) can
work (or rather, I do not believe that this notion corresponds to a
solution of the problem).
It really depends
On Wed, 12 Jan 2011, Rob Seaman wrote:
Sloshing the timezones around willy-nilly by every regional government
on Earth is not a solution to establishing the underlying common
timescale.
Of course not, that's backwards. The common timescale is the basis of
timezones, not the other way round.
On Sat, 29 Jan 2011, Stephen Colebourne wrote:
Thus, no matter what, the Sun must peak at midday and it be night at
midnight, with adjustments to ensure that based on time-zones. Since
stopping leap seconds breaks that basic principle, it became
unacceptable.
Actually the sun doesn't peak at
On Sun, 30 Jan 2011, Stephen Colebourne wrote:
The idea that midday or midnight would cease to have the same meaning to
an average person is horrid and I would suggest something that some
politicians would get very worked up about.
In other words, I flat out don't believe that the tinkering
On Sat, 29 Jan 2011, Warner Losh wrote:
A second minor point: TAI does not exist before this point. Proleptic TAI is
used, but more often TT is used for epochs prior to the present. I'd just
note here that a proleptic TAI is used for dates prior to the 1958 epoch.
How is proleptic TAI
On Sat, 29 Jan 2011, Finkleman, Dave wrote:
Ken, John Seago, and I delivered a paper to the AAS last August that
includes many of the thoughts in this thread.
Is a copy of the paper available online?
Tony.
--
f.anthony.n.finch d...@dotat.at http://dotat.at/
HUMBER THAMES DOVER WIGHT
On Mon, 31 Jan 2011, Steve Allen wrote:
http://www.agi.com/downloads/resources/user-resources/downloads/whitepapers/DebateOverUTCandLeapSeconds.pdf
Thanks!
Tony.
--
f.anthony.n.finch d...@dotat.at http://dotat.at/
HUMBER THAMES DOVER WIGHT PORTLAND: NORTH BACKING WEST OR NORTHWEST, 5 TO 7,
On Tue, 1 Feb 2011, Mark Calabretta wrote:
In the very distant future when the mean solar day is 86401 SI
seconds long (or hopefully well before that), the pretence that
the day is only 86400 SI seconds long, with its reductio ad
absurdum result of a leap-second-per-day, should hopefully
On Tue, 1 Feb 2011, Mark Calabretta wrote:
We all deal every day with a non-uniform and variable radix counting
system - 30 days hath September,
However the Gregorian calendar can be implemented in a few static lines of
code, which is orders of magnitude less than is required to handle
On Tue, 1 Feb 2011, Michael Deckers wrote:
As far as the civil uses of time scales are concerned, it is actually
UTC rather than TAI that is currently more predictable: I can
predict with great certainty that I shall attend a group meeting
when UTC will be 2012-01-30 + 09 h, but
On Wed 2011-02-02T16:47:22 +, Stephen Colebourne hath writ:
- the current definition of the SI-second was ratified in 1967
And clarified in 1997 and 1999.
Tony.
--
f.anthony.n.finch d...@dotat.at http://dotat.at/
HUMBER THAMES DOVER WIGHT PORTLAND: NORTH BACKING WEST OR NORTHWEST, 5 TO
On Wed, 2 Feb 2011, Finkleman, Dave wrote:
That a minute is 60 SI seconds except when there are 61 applies to some
other kind of minute than an SI Minute.
8601 doesn't define such a thing as an SI minute :-)
I believe that the SI second is defined at sea level in an Earth Fixed
reference
On Wed, 2 Feb 2011, Warner Losh wrote:
Perhaps even an extension to ntp and 1588 to allow this information to
ride along in those protocols.
I think that because UT1 is such a niche timescale, and because DUT1 is
calculated and updated relatively infrequently, that it would be simpler
to leave
On Wed, 2 Feb 2011, Gerard Ashton wrote:
The point below should be
* definition: UTC-1972-day - a duration of 86399, 86400, or 86401 seconds.
On 2/2/2011 8:50 PM, Stephen Colebourne wrote:
* definition: UTC-1972-day - a duration either 86400 SI-seconds or
86401 SI-seconds long
To be
On Wed, 2 Feb 2011, Steve Allen wrote:
It is mean because until the 17th century there was no concept that
any chronometer could be more stable than the diurnal passage of the
stars overhead.
Much later than that! After all that's what the longitude prize was all
about.
Unless you are
On Fri, 4 Feb 2011, Mark Calabretta wrote:
On Thu 2011/02/03 11:05:01 -, Tony Finch wrote
in a message to: Leap Second Discussion List leapsecs@leapsecond.com
In order to see the analemma you need to know the equation of time.
You only need a clock and knowledge of the length of a mean
On Thu, 3 Feb 2011, Clive D.W. Feather wrote:
michael.deckers said:
Very interesting, thanks! The double leap second resurfaced
in the ISO standard for C in 1989.
However, this (and its adoption by reference into Posix) was due to a
misunderstanding by the people in WG14 at the
On 3 Feb 2011, at 20:15, Warner Losh i...@bsdimp.com wrote:
Sure, we can quibble about the details. I thought that since ntp/1588 are
used in places that might not have access to the wider internet it would make
sense to allow (but not require) them to distribute this information when
On Mon, 7 Feb 2011, Hal Murray wrote:
Doesn't it depend upon gravity (aka sea level)? Is that standardized?
Yes. The SI second is defined independent of any reference frame. The
TAI second is the SI second as realised on the geoid. There are other
timescales that are based on SI seconds in
On Fri, 4 Feb 2011, Steve Allen wrote:
But cesium chronometers became available at the very same IAU meeting
which defined UT2, and by the time cesium had been calibrated with ET
and UT2 it was already evident that cesium revealed the earth, and
thus UT2, was badly irregular.
I thought that
On Mon, 7 Feb 2011, Steve Allen wrote:
Until there is an ensemble of cesium chronometers not on the surface of
the earth there is no easy way to measure the potential depth to 1e-10,
so the corrections currently being used to compensate for the NIST and
PTB chronometers being about a mile
On Mon, 7 Feb 2011, Finkleman, Dave wrote:
This discussion exposes the fact that we don't all have to work in the
same reference frame or time system - as long as we understand what we
are using and make it clear to users.
Though the whole point of universal time is that it's the default
On Tue, 8 Feb 2011, Rob Seaman wrote:
Ian Batten wrote:
Knife-edge systems which rely on the correct application of high-grade
skills may suit people with The Right Stuff, but real-world
engineering has to function when the operators are merely average, or
tired, or distracted.
There
On Tue, 8 Feb 2011, Rob Seaman wrote:
I'd say that history is pretty quiet on timekeeping issues in general.
I think very highly of Dava Sobel's Longitude, but one book does not a
library make.
There's also Saving the Daylight by David Prerau. (The title has varied
a bit.)
Also Calendrical
On Tue, 8 Feb 2011, Rob Seaman wrote:
UTC is not civil time anywhere,
I understand that you wish to assert that local time == civil time.
But you also assert that computer networks worldwide must be
synchronized. Is this latter somehow not a civil function?
Civil usually relates to a
On Tue, 8 Feb 2011, Warner Losh wrote:
On 02/08/2011 14:39, Rob Seaman wrote:
C) As pointed out on numerous occasions in the past, these kaleidoscopic
timezones would accelerate quadratically just like leap seconds.
This problem isn't solved by this method either. True.
Except that
On Tue, 8 Feb 2011, Rob Seaman wrote:
B) Detailed expert knowledge would become necessary to answer even
simple questions of comparing both clock intervals and Earth
orientation questions either in a single place or across epochs and
locations.
We have that today.
We have a soupçon
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