Re: [LEAPSECS] future access to solar time?
Tony Finch said: > Well, no, not for more than half the year. I happen to be close to the > Greenwich meridian so my clocks currently show something close to mean > solar time (about 30 seconds fast, I think?) but that isn't true for most > people. Indeed. I live 1 minute 37 seconds east of the prime meridian - I'm probably closest to it of anyone on this list. > The clock on the wall tells the time for social > purposes, not for the position of the sun in the sky. Right. And that's without the equation of time coming into the, um, equation. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] leap minute or hour
Miroslav Lichvar said: > It doesn't even have to be a full-hour shift. Some countries use > timezones with offsets given in 15-minute resolution, True, though they're very rare. > so any software > used globally already has to support 15-minute shifts. Adding support > for 1-minute shifts in timezones might be easier than Y2K. I don't see the benefit of anything less than the current 15 minutes. People all round the world are used to clock and solar time differing by more than that (I think the record is about 3 hours), so why make things awkward for people? Stick with what people are used to, which is (mostly) shifts of an hour. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] leap minute or hour
Poul-Henning Kamp said: > Full hour shifts, on the other hand, can be done merely by changing > the time-zone, and they can be done through the normal political > process, aligned to recognized borders. Something I've been arguing for a long time. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Celebrating the new year a few seconds late
Jonathan E. Hardis said: >> There were experiments at NIST in the early days of TV to use the TV signal >> as a time dissemination source. It worked well, as coordinated with the NIST >> radio time signals. But it didn't turn out to be a practical solution. > > More specifically, the idea was to put a character code (like ASCII) in the > VIR (vertical interval reference) portion of the signal that would be the > correct time. There turned out to be little interest in the technology for > this purpose, but an alternate application made it big???closed captioning. Never mind "closed captioning" (which I presume is subtitles for the deaf). In the early 1970s the BBC worked on a complete multipage text information system put in the blanking space; this was announced in October 1972. The system had 999 addressable pages of 40x24 characters, with colour and simple graphics available. Often a single "page" would actually be a cyclic sequence of pages, changing every 20 seconds or so. Subtitles (on page 888) were just one use. http://teletext.mb21.co.uk/gallery/ceefax/ or google "Ceefax" for more information. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] more Windows 10 leap details
Steve Allen said: > Here is another blog post about handling of leap seconds in Windows 10, > including a link to video of Judah Levine at the NYSE decrying smearing. > > https://blogs.technet.microsoft.com/networking/2018/10/17/leapseconds-for-the-itpro/ Reading this, it appears they provide a mechanism for inserting a leap second for testing purposes (good), but I can't see any description of that mechanism (bad). -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Negative TAI-UTC
Tom Van Baak said: > Yes, of course. This is not the 1960's where saving a byte was an all-day > decision. The spec is clear. Follow it. Actually, some of us work in fields where every byte is still expensive. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
[LEAPSECS] Negative TAI-UTC
Looking only into the future, not historical data, what do people think the probability is that TAI-UTC will ever be negative? Should data structures be designed to handle this case or not bother? -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] BBC radio Crowd Science
(numbered 60) to some minute. Conversion from UTC to TAI is the easier of the two: to convert UTC time t to TAI: E = Delta_at_UTC (t) L = linearize (t) + E D = int(L / 86400) H = int((L - D * 86400) / 3600) M = int((L - D * 86400 - H * 3600) / 60) S = L - D * 86400 - H * 3600 - M * 60 (The last four lines, obviously, are the inverse of the linearization process.) We might think that conversion from TAI to UTC is done in exactly the same way: to convert TAI time t to UTC: E = Delta_at_TAI (t) L = linearize (t) - E D = int(L / 86400) H = int((L - D * 86400) / 3600) M = int((L - D * 86400 - H * 3600) / 60) S = L - D * 86400 - H * 3600 - M * 60 In fact, this works *nearly* all the time, because nearly all the time there is exactly one D:H:M:S value that linearizes to L and a simple check shows it gives the right answer. For example, looking at the first line of both cases A and B above: t = 99:23:59:56.5 E = 42 L = 8640038.5 D = 100 H = 0 M = 0 S = 38.5 Result: 100:00:00:38.5 TAI. If you track through cases A and B, you'll find that this always gives the right answer with a single exception in case A. Here, both 100:00:00:42.5 TAI and 100:00:00:43.5 TAI will generate the same value of L (864.5), which then converts to 100:00:00:00.5 UTC; this is wrong for the first of the two. However, it turns out to be very easy to both detect and correct for this case. The correct algorithm for converting from TAI to UTC is: E = Delta_at_TAI (t) F = 1if Delta_at_TAI (t + 1) > E 0if Delta_at_TAI (t + 1) <= E L = linearize (t) - E - F D = int(L / 86400) H = int((L - D * 86400) / 3600) M = int((L - D * 86400 - H * 3600) / 60) S = L - D * 86400 - H * 3600 - M * 60 + F (F is 1 if and only if the UTC time is XX:XX:XX:60.X) -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] alternative to smearing
Preben Nrager said: > If you don't care about Christ, and the church, I can understand why you > treat all timescales alike. But if you really care about the fundamental > timescale of science and society, then I don't see how you can ignore the > time of the incarnation. If you really want the fundamental timescale of society, then your zero point should be the date of the first creation of the world by his Supreme Noodliness the FSM. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] alternative to smearing
Tony Finch said: > It's also worth remembering that with Old Style dates the year started on > the 25th March. It's very easy to be accidentally anachronistic :-) Sometimes and some places. This is why 1751 (not 1752) was the shortest ever year in England but not in Scotland. Wikipedia notes "At various times and in various places throughout medieval Christian Europe, the new year was celebrated on Dec. 25, the birth of Jesus; March 1; March 25, the Feast of the Annunciation; and Easter.". -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] alternative to smearing
Preben Nrager said:
> Let's say Newcomb envisions negative JDs, and astronomy thus uses the JD
> system. Astronomy then have two different "eternal" timescales, with two
> different starting points for zero: The one is the proleptic gregorian
> calendar, represented by ISO 8601, with the starting year zero, and the
> other the JD system, with the starting day zero.
Yes. So what?
> I understand the need in astronomy, and computer science, for a continuous
> timescale, and I understand that continuous days, and fractions of days, is
> better suited that need, than continuous
> years:months:days:hours:minutes:seconds. But I don't understand how
> astronomy can cope with two different starting points for zero.
Very simply. If I write "JD 12345678" I mean a specific day (pace the
issues about which definition of "day" is being used). If I write
"1234-05-26 PG" (or whatever abbreviation is used) I mean a different
specific day. Conversion between the two is a simple algorithm.
> The
> beginning of time must be a beginning in time,
We aren't talking about "the beginning of time". We're talking about the
arbitrary zero point for a date labelling system. There is absolutely no
problem with two systems having two zero points.
For that matter, the actual definition of year numbers in ISO 8601 is - or
was last time I read it - that year 1875 is the year that the Treaty of the
Metre is signed. In other words, it's not even defined by where zero is!
> and I don't see how
> astronomy can have a day zero, that is different from the year zero. The
> zero point in time must somehow be the same for both the daily, and the
> annual timescale.
The reference point of the Celsius temperature scale is the melting point
of pure H2O at an arbitrary atmospheric pressure whose value I forget. The
reference point of the Kelvin temperature scale is the thermodynamic
minimum possible temperature ("absolute zero"). Nothing stops people using
both even though they have different zero points. And that's without
mentioning Farenheit, Rankine, Romer, Newton, Delisle, Reaumur, Leiden,
Wedgwood, and Gas Marks.
Time is no different. Provided that we know the conversion algorithm, there
is absolutely no problem with having multiple systems. See the book
"Calendric Calculations" for further details.
> The way I see the JD system being used in astronomy, it is as the
> fundamental timescale. The number of JD is related to the days in either
> the julian or the gregorian calendar, but the proleptic gregorian calendar,
> with year zero, is not really being used. I don't know if that is because
> Christmas day (December 24/25), and other important days, are not the same
> JD in the julian, and the proleptic gregorian calendar,
1234-12-25 Julian and 1234-12-25 proleptic Gregorian are different days.
Just as 2017-12-25 Julian and 2017-12-25 Gregorian will be different days.
So what?
> but either way, the
> zero point in time must be the same for both the daily, and the annual
> continuous timescale.
Why?
> I propose to reform the JD system with a new system of proleptic gregorian
> days GD. The proleptic gregorian calendar, with year zero, shall be the
> fundamental timescale, and in that calendar each year has either 365 or 366
> days, in accordance with the gregorian leap year rules. Year 0 is a leap
> year.
>
>
> The new system of GD shall like JD count the days from noon to noon. But
> the zero day shall not be JD:0. The zero day of GD shall be the day from
> -0001-12-31T12:00 to -01-01T12:00. That day is JD:17210159, so my
> reform will be the removal of 17210158 days from JD, to create GD.
So your GDs are just JD minus 17210158? That shows that you can cope with
two different zero point with no trouble.
> With the new timescale I propose, negative years and negative days will
> always be the same,
Okay.
> and that I think is important.
Why?
Anyone who's dealt with AD, AM, and AH dates knows that a date can be
positive in one system and negative in another. That's not a problem -
there's nothing magical about negative year numbers.
You might just as well argue that we should use LCDs, where the zero point
is the Mayan Long Count date 0.0.0.0.0 (-3113-08-11 PG).
--
Clive D.W. Feather | If you lie to the compiler,
Email: cl...@davros.org | it will get its revenge.
Web: http://www.davros.org | - Henry Spencer
Mobile: +44 7973 377646
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Re: [LEAPSECS] alternative to smearing
Tom Van Baak said: > Because most people don't live in Greenwich Greenwich isn't the only relevant place. I think I'm probably the person on this list who lives closest to the Prime Meridian, at 0.027066 degrees east according to Google Maps (I used to live at 0.011605 but moved house). I'm in favour of using "the existing noon-alignment knob (time zones) to keep noon at 12" if relevant local authorities want it to be (a lot seem to want noon at 13). -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Time math libraries, UTC to TAI
Michael.Deckers. via LEAPSECS said: > It is the Julian day numbers used in astronomy that > take integral values at noon epochs -- but they have nothing to do with > the Julian calendar, except perhaps for the origin of the name. Not even that - I thought Julian days were named after some astronomer or other. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Greetings from an intercalary second
Steve Summit said: > But on the wire it was: > > Date: Sat, 31 Dec 2016 18:59:60 -0500 That's what mutt showed me (I'm running sendmail on my own FreeBSD box). -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] 2016 is not tied for second longest year ever
Warner Losh said: > I'd think that 1712 in Sweeden was the longest year with 31708800 SI > seconds (give or take a few hundred milliseconds, my data-sniffing fu > isn't up the challenge of digging through the historical data to find > out how many). That was a double-leap-year. What about 708 AUC, with 15 months and 445 days? Surely that completely trumps 1712? -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] [time-nuts] Leap second to be introduced at midnight UTC December 31 this year
Tom Van Baak said: >> Does your proposal allow for a Zero leap second > Nope, LSEM avoids the zero leap second situation. That's the idea: to always > have a leap second. Either an add or a delete, at the end of every month. The > beauty is that it wouldn't violate how UTC is already defined. Leap seconds > would become a monthly normal instead of a rare event; that is, a regular > pain in the ass instead of an exceptional pain in the ass [1]. A problem is that each year requires either a zero change or a 2 or 4 second change. Not one second per year. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Google, Amazon, now Microsoft
Tom Van Baak said: Can you send me a definitive URL with global TZ rules so I can grep|sort|uniq to get a feel for when DST transitions occurs? The following database: https://www.iana.org/time-zones is about as definitive as you will find. I guess I thought it always was 2 am local (which implies jumps from 02h-03h and 02h-01h). That is very definitely *NOT* the case. Also, possibly related, do you know of any place where DST is +/- 2 hours instead of +/- 1 hour? I ask because the still-in-development PE (phase encoded) WWVB format appears to allow for such a (non US legal) transition. I can't quite tell if it's a bug or typo or spec. Look in the same database. The UK certainly used to have two changes each way in the year (that is, from GMT to GMT+1 to GMT+2). Some places only change by 30 minutes. I can't say I've heard of anywhere jumping 2 hours in one go on a regular basis, but I won't claim it's never happened. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Google, Amazon, now Microsoft
Tom Van Baak said: Oh, I wasn't thinking of cheating and adjusting timezones with a mouse click. For maximum photo effect, I was planning to drive my mobile (car) time lab across two time zones the night of June 30 and catch two Azure leap seconds. Timezones are too wide to hit three in under 2 hours. I'm sure there must be places where 3 or more zones meet. Let's see: * Russia/Finland/Norway triple point. * 6 places in Russia and 3 on the border where 3 zones meet. * Turkey/Iraq/Armenia triple point. * Lots of other places where three countries meet. And in the summer Arizona is UTC-7, New Mexico is UTC-6, and the part of Mexico immediately south of NM is UTC-5. That ought to be doable in an hour. Ah, there's almost a four-way meet. Afghanistan (UTC+4.5), Tajikistan (UTC+6), and China (UTC+8) meet at a point and, less than 20 kilometres south of there, is the China/Pakistan (UTC+5) border. There don't seem to be roads, but an off-road vehicle ought to be able to do it in an hour. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Google, Amazon, now Microsoft
Pierpaolo Bernardi said: http://eur-lex.europa.eu/legal-content/IT/TXT/?uri=CELEX:32000L0084 By the way, I noticed only now that the English text says 01:00 GMT, while the Italian text says 01:00 Tempo Universale. It's worse than that. Of the 22 official texts: BG, CS, EL, EN, ET, FI, HU, LT, LV, MT, SK, and SV use terms equivalent to Greenwich, Greenwich Time, or GMT. DE, ES, FR, IT, NL, PT, and RO use terms equivalent to Universal Time. PL says uniwersalnego (GMT). DA and SL use UTC. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Letters Blogatory
Poul-Henning Kamp said: We have a saying in danish Skoma'r bliv ved din læst which translates to Cobbler stay at your workbench. The English word is last: The cobbler should stick to his last. Almost certainly with the same derivation. The fact that he is a lawyer seems to have nothing, if anything to do with his personal opinion on leap seconds. In other words: Yeah, he's entitled to his opinion, just like everybody else, but he doesn't have any special standing for his opinion, which as others have pointed out, interfaces badly with reality. Exactly. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] The definition of a day
Peter Vince said: Surely it would be better to allow civil time to run smoothly from atomic clocks, and give ourselves a few hundred years to quietly consider how to correct the slow drift that has reached the same order of magnitude as the analemma effect, which we regularly ignore and/or aren't even aware of? There's already a proposal for solving this - one that I support. That is to allow each polity to decide when the drift is large enough to be annoying and then make a 1 hour change to their (local time - UTC) delta value. For those polities that make a twice-yearly change anyway, this could be done by omitting one such change. So, let us suppose the year 2600 is when the drift reaches the annoying point, and let us suppose the EU is still in existence. By then the sun will reach its highest point at about 12:45 UTC. So at this point the EU announces (a few years ahead) that the normal autumn shift back of the clocks will not happen. From autumn 2600 onwards, the UK will observe UTC+0100 in the winter and UTC+0200 in the summer; France will observe UTC+0200 and +0300, and so on. Dealing with local time changes as you cross borders is something people are used to, as is the fact that the amount of change varies both within the year and from year to year. So there's nothing new for people to get used to. Simples. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] DNS examples
Brooks Harris said: No, you need to use a library that's already been written to do the job. Takes 10 seconds or so. What library that's already been written to do the job are you referring to, specifically? I don't know, not having investigated. But if it's that big a deal, I'm sure someone has already produced one. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] DNS examples
Steffen Nurpmeso said: | Well. PHK follows the IERS format which uses the 1st of the month | after the leap second, i.e., the second after the leap occurred. | |This is an implementation detail. PHK???s choice is as good as the other. And i disagree with that. The ISO C(99) standard doesn't offer a JDN-TO-Gregorian and vice versa calculation. There is the well-known algorithm from Communications of the ACM, Vol 6, No 8, but it is not in the standard. Irrelevant. The C Standard, in general, holds only those facilities which either can't be expressed in terms of the Standard language itself (e.g. printf) or which are extremely common and therefore benefit from having a standard name (e.g. strcpy). Converting JDN to Gregorian fits into neither of these categories, so it does not belong in the C Standard. So in order to calculate the actual date where the drift adjustment occurs you have to face a very elaborate conversion. No, you need to use a library that's already been written to do the job. Takes 10 seconds or so. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] the big artillery
Tony Finch said: minutes and seconds are fractions of 60 and have been so since babylonian times for minutes and since 13-mumble for seconds. The etymology is actually helpful in this case rather than misleading as etymologies so often are. minute is short for pars minuta prima, the first small part second is short for pars minuta secunda, the second small part And I've seen third and fourth, with the obvious meaning, used in old documents. But etymology doesn't override present meanings. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] the big artillery
Harlan Stenn said: I'm still thinking the answer is leave existing 'names' alone - if you want TAI use TAI. If you want UTC, use UTC. If you want something new, call it something new. If people are using a defined name for a defined purpose and it works for them, leave it alone. If people are using a defined name for a defined purpose and it does not work for them, this group needs to come up with a new name for the thing they think will solve their problems. The problem is that some people use UTC to mean TAI plus adjustments to keep it less than a second from UT1 while other people use UTC to mean the basis of legal time here. For the second set, using a new name for a different concept doesn't help. There are good reasons for wanting legal time to be TAI+n+local offset, where n is a constant (somewhere around 35?) that never changes in the future and local offset is chosen by the relevant lawmakers and is normally a multiple of 15 minutes. If you accept that these reasons override those for keeping leap seconds, then a name change won't make it easy. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Do lawyers care (know) about leap seconds?
Gerard Ashton said: Businessmen can keep whatever time they like for internal use, but whenever a businessman communicates with a customer or another business, the courts will interpret any times stated as being the legal time of the applicable jurisdiction, although in many cases the businessman and the other parties have the option of agreeing to a different time scale. About 3 years ago I gave a paper on this topic to a law conference. One of the things I suggested then is that laywers should start adding choice of timescale clauses to the choice of law clauses they already use. Whether anyone has actually done so, I don't know. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Do lawyers care (know) about leap seconds?
Hal Murray said: How many contracts worry about seconds? Ones to deal with electronic trading, domain name registration, and such topics. I think it's common for contracts to start one minute before or after midnight to avoid an English language ambiguity. Things like midnight Monday might be the midnight at the start of Monday or the midnight at the end of Monday so contracts usually use 00:01 or 23:59. A bit of googling found a web page describing that, but I don't know what they teach in law schools. They didn't suggest it on my law course. I found a law case (sorry, no cite) that was decided on a matter of 8 seconds - from memory, an email sent 8 seconds after a midnight deadline. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Leap second relationship to ISO 8601
Tony Finch said: However for events in the future (meetings etc.) you need to record a time and a place, because the UTC offset and time zone rules are not predictable. More precisely, the accuracy of predictions varies. (I'd have a lot of confidence in the 2005 offsets for England. Rather less for those in Palestine.) -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Leap second relationship to ISO 8601
Brooks Harris said: An organization I work with has been using a web-based meeting scheduling calendar that gives meeting date-time notifications. Recently it has been announcing meetings as, for example - When: Wednesday, September 24, 2014 11:00 AM-12:30 PM. (UTC-05:00) Eastern Time (US Canada) Of course Daylight is in effect on the east coast, so its completely wrong. What is intended is 2014-09-24T12:00-04:00 (noon, Eastern Daylight Time). Microsoft's calendaring stuff does that. I keep getting stuff that says it's at (say) 10:00 UTC, plus the UTC offset doesn't take account of daylight savings time, when what it means is 10:00 BST. Even worse is the ones that say 10:00 UTC+01:00, which actually mean 09:00 BST. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Leap second relationship to ISO 8601
Brooks Harris said: In particular, 8601 implies use of offset from UTC, as indication of local time, but conflates this with Daylight Savings. No, it doesn't. It uses offset from UTC as an indication of, wait for it, offset from UTC. For example, a date and time in New York City might be represented as 2014-07-04T00:00:00-05:00 which misses the fact that Daylight was in effect, or 2014-07-04T00:00:00-04:00 which misses the fact the the fixed timezone offset is -05:00. No. 2014-07-04T00:00:00-05:00 means the start of the day according to a clock observing an offset of -5 hours. Someone in New York City might have such a clock if they needed to correspond with Chicago. 2014-07-04T00:00:00-04:00 means the start of the day according to a clock observing an offset of -5 hours. That is the offset typically observed [1] in New York City on that date. The use of an offset does *NOT* imply either a time zone or the presence or absence of an bi-annual shift. My office in Cambridge has clocks on the wall showing the time in offsets -07:00, -04:00, +01:00, +02:00, +05:30, and +08:00, because those are the ones we regularly communicate. Though they all show different numbers, they are all showing the same time. [1] But see R.v Haddock [1967] BBC 1.4. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Solar time: From mean solar days, to mean solar years
Warner Losh said: Absolutely. We get leap days right because we don?t have to hear from the pope?s astronomers every year to know if it will be a leap year or not. We know for thousands of years. And note that it was exactly that problem that led Caius Julius to reform the calendar in the first place. [...] Another thing we could do is [...] Or we could decouple UTC from GMT and allow each country to decide when to change its offset. That subsumes the whole problem into the summer/winter time switch, or the move past the International Date Line switch, that the whole world knows how to handle, even if they don't all do it. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Definition of Standard time - Brooks Harris
Tony Finch said: But not mine. standard time is to be contrasted with local time. Both GMT and BST are standard time in the UK. The relevant distinction is from the late 1800s, between local mean solar time and time based on a standard meridian, as in railway time. Right. But to be honest, I don't hear either term used very often in the UK, where we (almost) only have one time zone. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Definition of Standard time - Brooks Harris
Brooks Harris said: Wikipedia (not always an authoritative source) Standard time http://en.wikipedia.org/wiki/Standard_time states: Where daylight saving time is used, the term standard time typically refers to the time without the offset for daylight saving time.. That is consistent with my understanding of Standard time. But not mine. standard time is to be contrasted with local time. Both GMT and BST are standard time in the UK. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] happy anniversary pips
Warner Losh said: Yes. I've never been able to understand why facing the guts of this problem has been evaded. Its a great computer-science project - it should be fun! The problem stems not because one person can't climb the complexity hill to get it right: several have. The problem comes more from the large numbers of people in my industry that have failed to climb the complexity hill due to apathy, incompetence or both. Or they (or their bosses) have done a cost-benefit analysis and concluded it's not worth fixing. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] happy anniversary pips
Hal Murray said: I don't pay attention to summer time in Europe. How often do things change over there and/or how much notice do people get when the rules are changed? The EU has standard rules defined in a Directive. The present Directive is 2000/84/EC and was published in the Official Journal on 2001-02-02. It took effect from March 2002. That Directive didn't actually change the rules; the last one that did was 97/44/EC, which changed the autumn rule from fourth Sunday in October to last Sunday in October. This appeared in the OJ on 1997-08-01 and gave the rules for 1998 to 2001 inclusive. So we're talking a year or so lead time. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] happy anniversary pips
Brooks Harris said: D) Clarifying timezone guidelines, including standardizing international date line, UTC offset, and methods of Daylight instantiation Um, timezones are a political matter pure and simple. Who do you think is going to listen to you? -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Pedagogy Greenwich
Ian Batten said: The easternmost point of the London district of Greenwich is a the intersection of two roads, Maze Hill and Charlton Way. The coordinates are 51° 28.509' N, 0° 0.602' E I'm not sure what you're using as a definition of district. SE2 0AT is in the Royal Borough of Greenwich, and is 51° 28' 57.8442N, 0° 7' 15.0053E. There are places slightly east of there that are also in the Borough. Google Maps seems to think that the easternmost point of the Borough is the intersection of Brampton Road and Longleigh Lane. This is at 51.477106,0.123897. Streetmap (using the OS maps) agrees and gives me coordinates of: OS X (Eastings) 547590 OS Y (Northings)177498 Nearest Post Code DA7 5SE Lat (WGS84) N51:28:38 (51.477194) Long (WGS84)E0:07:26 (0.123860) LR TQ475774 -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Common Calendar Time (CCT) -Brooks Harris
Ian Batten said: Certainly, if Scotland does opt for independence (on current polling and betting it seems unlikely, but let's suppose) the pressure for England to move to CET will increase. There's some confusion as to whether the proposal would be moving the UK to UTC+1/UTC+2 as happened during the last war, or UTC+1 all year around, as happened in the experiment between 1968 and 1971, but on the assumption that the latter would have too many practical problems Apart from anything else, it would violate EU law. I don't see why UTC/GMT would have any relation to the Scottish referendum which, in any event, is only 9 months away and will be a dead issue (one way or the other) thereafter. Anyone so red-faced and UKIP-y that the designation of UK legal time as GMT or UTC mattered to them would be a lost cause for any sane political party anyway, so I don't see them mattering.The set of people who would vote Tory but would be tipped over into Farage-ism by the nomenclature for time is not a major political force. No, it's the political *impression* that it matters. Politics is mostly about appearances. Look at the unhappy history of the Coordinated Universal Time Bill. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] The Once and Future Time
Rob Seaman said: Systems, software and civilization depend on both interval time and Earth orientation time. In what way does civilization depend on Earth orientation time? Given that existing locations have local time several *hours* away from solar time, this seems unlikely. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Common Calendar Time (CCT) -Brooks Harris
Brooks Harris said: tm_sec + tm_min*60 + tm_hour*3600 + tm_yday*86400 + (tm_year???70)*31536000 + ((tm_year???69)/4)*86400 ??? ((tm_year???1)/100)*86400 + ((tm_year+299)/400)*86400 This is an *uncompensated-for-leap-seconds* Gregorian calendar counting scheme with an artificially imposed 1970 (the Epoch) origin. I like to call it the 1970 *barrier*. Why is it a barrier? Nothing prevents tm_year being negative; indeed, it's a signed type. But, CAUTION - not all implementations of gmtime() are equally good. I've compiled and tested many versions from the open-source community and many have smoking gun errors. Outright bugs don't help confidence in consistent implementation and contribute to the confusion. And that's *without* having to test for an event that only happens every year or two. Which is why software engineers (among others) would like to get rid of leap seconds. Maybe the way forward would be to introduce a new elapsedtime_t type that really does count seconds since the Epoch (to be used in any applications that require duration) and to deprecate arithmetic on time_t values (which is problematic around leap seconds). Yes, generally. Getting ANSI c and POSIX standards bodies to change their ways is an uphill battle. When I was on the ISO C (*NOT* ANSI c) committee, we looked at the issue. Then we asked the expert community (that is, you lot), to come up with a consensus proposal that we could look at. As far as I know, the committee is still waiting. (I *did* get the double leap second error removed from ISO C, meaning it vanished from POSIX as well. Everyone agreed that this had been a simple misunderstanding of something back when the first version of the C Standard was being written.) -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] presentations from AAS Future of Time sessions
Steve Allen said: What *has* been proposed, where I have seen it, is to remove leap-seconds, and leave the keep civil time in sync with the sun up to local governments who can mess with their timezones as they see fit. Right. And of the proposals on the table, this is the one that seems to me to be the most practical. This notion leaves open the question of the name UTC. In particular, can the delegates to the ITU-R RA be persuaded to vote for a new version of TF.460 if they are aware that the new wording will change the legal definition of the word day in every country which has adopted UTC as its time scale? I don't know who will vote for what. Removing future leap seconds won't change the legal definition of the word day anywhere. What it does mean is that, in countries using UTC as part of the legal definition, the centre of the night will drift away from 00:00 before stepping back again. In effect, it will vary in the same sawtooth way that midnight varies around 00:00:00 with leap seconds. This can be seen as an advantage or a disadvantage, depending on your view of things. Will the delegates from other nations simply reject a proposal which is rooted in and strongly pushed by the military needs of the USA? What's the basis of this assertion? -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 88, Issue 31
Greg Hennessy said: Dennis McCarthy once forwarded me an english translation of the Inter gravissimas, http://www.bluewaterarts.com/calendar/NewInterGravissimas.htm and it is utterly silent as to what to call the year before 1 AD. Indeed, it says nothing about how years are numbered, but assumes everyone already knows. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] inaugural effects of abandoning leaps
Steve Allen said: If without leap seconds the ITU-R regulations and recommendations become self-inconsistent then an unfortunate event happening within the day-long ambiguous interval coinciding with a change of insurance policies could be deemed to be covered by none, one, or both policies. In that case sane falls victim to corporate responsibility to the shareholder of insurers and insured. Lawsuits seem inevitable. We figured out how to fix that in 1750 (see 24 Geo.2 c.23 s.6). You may now stop panicking. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Testing computer leap-second handling
Michael Spacefalcon said: But with the latter approach, those citizens who happen to be on the wrong side will have their fundamental human rights violated by being subjected to a delta between true MST and civil time than exceeds 30 min, If you think that this is a fundamental human right, then you are sadly deluded. * DST is an abomination That's probably the only thing you and I will agree on. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Testing computer leap-second handling
Rob Seaman said: The issue (discussed many times previously) is to avoid introducing a secular trend into UTC. And, as also discussed, you have yet to show that the woman on the Clapham omnibus even cares. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Hetzner mail to customers: 1 megawatt more power due to leap second
Michael Spacefalcon said: Suppose that a rubberization scheme were officially defined as something like this: At such and such precise time, the length of the civil second changes from exactly one SI second to exactly 1.001 SI seconds. At such and such precise subsequent time, it changes back to exactly one SI second. So do civil speed limits change from 70 mph to 70.07 mph during that period? Just how much of our infrastructure currently depends on the assumption that the civil second is the SI second? Besides which, you still haven't solved the problem - distribution of the leap information is still a hassle and handling of the event isn't properly tested. What this rare event does isn't the main problem. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Calendar authority
Tony Finch said: Individual national governments don't have much authority to legislate calendars - the Easter Act 1928 is a nice example. Disagree. If the relevant Order had been made by now, the two public holidays we just had would be this weekend coming instead. And, if I understand the constitutional issues correctly, the Church of England would be celebrating Easter next Sunday. That sounds like sufficient authority. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Calendar authority
Markus Kuhn said: I don't think the authority of ISO to define what calendar we use is any higher than (say) the authority of Wikipedia on such matters. They both are merely widely-respected committees reporting on what the current consensus is. Indeed. This is clearly something in the remit of national governments. See, for example, 24 Geo.2 c.23 or the decision of the National Convention on 1793-10-24. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Lets get REAL about time.
Stephen Colebourne said: Interestingly, in JSR-310 I may end up representing a date as a packed form of day-of-month (5 bits) and epoch-months (59 bits). Month calculations are then easy. Oh? When is a month from Monday coming? What day is 4 months after the last day of next month? What about the antepenultimate day of next month? Explain your working in each case. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Lets get REAL about time.
Stephen Colebourne said: Oh? When is a month from Monday coming? What day is 4 months after the last day of next month? What about the antepenultimate day of next month? Explain your working in each case. Each of those three examples requires the day-of-week, The first does, but only because I didn't phrase it as When is a month from 30th January?, which is what I meant. The point of storing data in this form is that most queries of a date are for year, month and day-of-month. Similarly, most sets/adds, like 2012-01-31 + 1month require the year, month and day-of-month. In the format above, those calculations are easy. Okay, all of those three (as amended in the first case) are of that form: 2012-01-30 + 1 month 2012-02-29 + 4 months 2012-02-27 + 4 months and let me add: 2011-02-28 + 1 year -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Lets get REAL about time.
Tony Finch said: The usual way to deal with logic of this kind is to be explicit about whether you are counting from the start or the end of the month. I don't know if there is consensus on whether day-of-month overflows should saturate or carry... Indeed. Which is why it isn't easy, contrary to the previous statement. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Lets get REAL about time.
Stephen Colebourne said: OK, I mean easy in computation, you mean easy as in well-defined result. Well, of course. Everything to do with dates is easy in computation once you've defined what results you're after. (Well, easy in that there's nothing strange that needs coding or corner cases to catch. It's not like doing a network protocol where there's all kinds of random events sticking their nose in.) -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Multi-timezone meetings
Rob Seaman said: You've imposed the additional requirement that you can't have a primary timezone, for political reasons. Requirements are discovered, not imposed. This from the person who insists that a priori civil time must synchronize with the sun? -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Leap second on analog watch
Rob Seaman said: 'The clock is entirely accurate only once every five minutes. The rest of the time, the pendulum may seem to catch or stop, and the lights may lag or, then, race to get ahead. According to Taylor, this erratic motion reflects life's irregularity.' I presume 4 times an hour was referring to the five minute cadence, Yes: my memory was that it was every 15 minutes, not every 5. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Leap second on analog watch
Rob Seaman said: Exactly. The search space is a lot larger than explored so far. Consider a leap second modification to the Chronophage for instance: http://www.wired.com/culture/design/magazine/17-02/st_chronophage Bear in mind that this is a clock that only shows the correct time 4 times an hour. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Lets get REAL about time.
Michael Sokolov said: What people like PHK fail to grasp is that a whole ton of applications absolutely DO NOT CARE how many Cs-133 transitions happen to occur in a given *civil* time interval, all they care about is a bijective mapping between their timestamps and *official civil time*. Agreed. Each (micro-)nation should indicate its official time with an analog clock (i.e., one with rotating hands, not digital) on the wall of a government building specifically to drive the point home that notations like 23:59:60 are not acceptable. This non-scalar notation is the real fundamental problem with UTC in my eyes, Total nonsense. (Nitpick: it's not non-scalar, it's non-uniform.) If that were a valid argument, then we wouldn't have different numbers of days in the month because you couldn't have a day-of-month hand on a clock. Yet clockmakers and the general public seem to have coped. If leap seconds were predictable (say they were exactly one every 18 months for the next century) it would be perfectly practical to build an analogue clock that had 61 divisions on the dial carrying the second hand, and which jumped the 60 position in most minutes. i.e., they should not pretend to have any relation to time-as-in-physics and should merely represents particular points in the course of analog civil time, i.e., particular angular positions of the rotating hands of the official clock on the wall of a government building. An indication that Mary Q. Public's subscription expires at 2022-07-25T19:41:42 UT1 is perfectly precise and unambiguous regardless of how many leap seconds occur between now and then. Except: (1) the notation 2022-07-25T19:41:42 UTC is equally precise and unambiguous when it happens; (2) since you don't know how much the earth will slow down in the next 10.5 years, you can't (easily, if at all) build a clock that will rotate the correct number of times; (3) neither UT1 nor UTC is civil time (though civil time may be based on one or the other). On the other hand, the *civil* timekeeping requirements can be very stringent. The example of expiration of subscriptions that Keith has brought up is a very good one: I like the idea of the moment of subscription expiration far in the future being defined very precisely *in relation to official civil time*, which for the Republic of New Poseidia is currently UT1. But in the real world it *isn't* that predictable. Let's take that subscription you mention. Under English law that time - without the UT1 tag - would be interpreted as BST, since under the Summer Time Act all times in July are to be interpreted as BST unless specifically mentioned. Right now BST means GMT+1 (for some meaning of GMT I'm not going to debate right now). But perhaps Labour come back into power in 2015 and decide to move us all to the same time as France and Germany. At which point BST will mean GMT+2. So never mind the 7 or 8 leap seconds - we can't even predict duration to within an hour. And that, I think, matches Tony Finch's point: for many things you don't care about the interval, you care about the end time in the *relevant* time zone. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Lets get REAL about time.
Rob Seaman said: It is already commonplace. Well, no. The geographic center of California is about exactly 8 hours (120 degrees) west of Greenwich. Los Angeles is a couple of degrees East and San Francisco a similar distance West of this meridian. Even for California plate tectonics can be ignored, and PST will always remain naturally 8 hours from GMT. Wrong. Yes, the mean solar time for 120 west will always remain naturally 8 hours from the mean solar time for 0 east/west. But it could well be that neither of those is the civil time for anywhere. Consider China. It decided that the civil convenience of keeping the whole country on one time zone was more important that the civil convenience of having the fictional mean sun be at the zenith at 12:00 everywhere. So even though it stretches from 73 east to 135 east, it uses the time zone of 120 east throughout. It is quite possible that a future USA government might decide that this same balance of civil conveniences has swung, and decide to move the whole country to the time zone of 90 west throughout. At that point PST will be, in essence, what you now call CST, and more to the point will be only 6 hours from GMT. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Lets get REAL about time.
Keith Winstein said: Hmm, in practice I think the plan to simply fail with an error is going to be a non-starter. Plenty of applications need to record dates more than six months in the future; e.g. in a calendar program, the user will want to schedule a meeting for August 1, 2012, from 9 a.m. EDT to 10 a.m. EDT. Actually, let's suppose it was March, not August. The user probably wants to schedule a meeting for 26th March 2013, 09:00 ET to 10:00 ET. Now the user doesn't care at this point whether ET is EST or EDT. If the changeover date changes between now and then, they want the appointment to remain ET. The program will want to do all the normal things -- calculate the duration of the meeting, how far in the future it is (so it can put it in sorted order along with the other events of that day), etc. Right. And they want all the ET events sorted by ET, irrespective of whether daylight saving time is in effect or not. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] ISO TC 37
Ian Batten said: However, it's somewhat disingenuous to claim that UTC as constituted meets this requirement, but UTC without leap seconds doesn't. S(9) doesn't say GMT +/- 1s, it says GMT. Why is one second's error bar axiomatically OK, while 1 minute, 1 hour, etc, not? The legislation specifies a timescale. The assumption that +/-1 1s is acceptable is a matter for case law, which as yet hasn't arisen. The assumption that +/- 1min isn't acceptable is not acceptable is also a matter for case law, which as yet hasn't arisen. I am aware of case law where a difference of 8 seconds between clocks was relevant. That's the shortest interval I've seen so far in my searches. (In general I'd agree with you: the permitted error is a question for the courts as and when it comes up.) If people wish to argue that the '78 Act requires GMT (and, note, the act only relates to the interpretation of other legislation, not to civil contracts or what your watch says) When I gave a paper on this at a law conference, it was suggest that - should this ever be a problem - lawyers would simply start adding choice of time clauses to contracts, just like they add choice of governing law clauses. Also note that it's routine to put the time zone into contracts where that is likely to be relevant. (It's odd to note that while the Interpretation Act only talks about other Acts, the Summer Time Act refers to any enactment, Order in Council, order, regulation, rule, byelaw, deed, notice, or other document whatsoever and doesn't seem to recognize the possibility that someone might explicitly put a time zone other than GMT/BST, apart from the exemption for astronomers.) -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] while we wait...
Poul-Henning Kamp said: Here is a nut-cracker much better than a Danglish split infinitive: http://www.agile-news.com/news-560573-Time-who-will-vote-on-the-side.html | King Charles II appointed Donald Di De Yue Hanfu as Chief Astronomer | Royal John Flamsteed will be rotating in his grave. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] ISO TC 37
Rob Seaman said: Who has an actual requirement for an approximation of UT to 1s? Almost everybody, Oh? I need an approximation of civil time to somewhere between 30s (when catching a local train or watching a television programme [1]) and 5 minutes (when attending an internal meeting). I have no requirement for any approximation to UT at all. Not even for lighting-up time; I put my car headlights on when it starts to look dark or when I see the sun near the horizon. I suspect the vast majority of people are like me. [1] But often I'll let the DVR record it automatically, then watch it a while later when I can skip through the adverts and/or boring bits. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Straw men
Ian Batten said: You cannot set up a bijection between successive 1s timestamps of UTC and successive valid 1s timestamps of UK Civil Time, because the civil timestamps between 01:00:00 and 02:00:00 on the fourth Sunday in October each map to two distinct UTC timestamps, as they are repeated in the sequence of UK Civil timestamps. Therefore UK Civil time is not mean solar time. (1) I'm not convinced that's correct, since there's an implied labelling of whether any given timestamp is in the period of summer time or not. Note that, in the Act, the period of summer time is defined using GMT at both ends. So the last timestamp is 02:00:00, but that is implicitly summer time since it's defined as being the last one because it is one o'clock, Greenwich mean time. (2) Not last year. The fourth Sunday in October was the 23rd. BST ended on the 30th. It's an interesting argument, though. I might try it on some lawyers. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] China move could call time on GMT
Warner Losh said: More to the point the entire notion of playing musical chairs with the worldwide timezone system [...] An hour every 10 years is 360 seconds a year, which is 20x faster than UTC can tolerate as it is defined today. Let's turn it around. UTC as defined today can cope with up to one leap second per month, or 12 per year. Any alternative proposal therefore needs only cope up to that limit as well (otherwise we are comparing apples with oranges or, if you prefer, are tilting the playing field). 12s/yr is 1 hour every 300 years. Therefore the musical chairs involves a *possible* change every several lifetimes. To put this in perspective, in the UK we're talking about further away than the introduction of the Gregorian Calendar with its 11 day shift and two consecutive years of unnatural length (282 and 355 days). In half that period we've moved from local mean solar time to GMT to summer time to double summer time to back again to BST to summer time again to something like 11 different rules for the shift date to a proposed permanent one-hour change for political and economic reasons even though it takes us *away* from the sun. If paying the price of an additional one-hour shift in 12 generations time is the price to pay for getting rid of leap seconds, I'd happily pay it in a heartbeat. It all comes down to what time on the clock should tell us: earth angle (eg, where the sun is) or elapsed time since an epoch. This whole issue boils down to that. Indeed. But Rob *defines* time as earth angle and then tries to tell us we're breaking the whole world. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Straw men
Rob Seaman said: Redefining UTC will break things immediately in astronomy and aerospace and related applications. False. It might break them at the point that |DUT| 0.9s. Or it might not. But it won't break them until then, which could easily be some years away. And it will leave any purely atomic timescale many minutes or hours in error at a future epoch with no plan for mitigation. They won't be in error - that's another of your misrepresentations. They will be different to UT, deliberately. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] China move could call time on GMT
Ian Batten said: or less correctly on DCF77 being civil time for most of the remainder of the EU, I was going to nit-pick that most, but I think you're correct. Of 27 countries and ignoring summer time issues: * 12 are in zone 1 * 8 are in zone 2 [BG, CY, EE, FI, GR, LT, LV, RO] * 2 are mostly in zone 1, with all of the EU parts in zone 1 [DK, NL] * 2 are mostly in zone 1 [ES, FR] * 2 are mostly in zone 0 [GB, PT] * 1 is in zone 0 [IE] The four microstates are all in zone 1. The five candidates are in 0, 1, 1, 2, and 2. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Straw men
Rob Seaman said: You keep trying to cook the process so that it only winds up with your solution. I am not trying to cook the process. The assertion of the notion that timezones will magically fix the problem is rather a confirmation of my point. There would be no problem, no engineering requirement demanding a fix, if time-of-day weren't the same thing as mean solar time. That is a requirement. It is a fact about the problem space. If you're not trying to cook the process, then stop making this mis-statement. time-of-day, as just about everybody uses the term, means time on the clock defined by my local jurisdiction. There is *NO* requirement that this be the same as mean solar time. It may be the case in some countries at the moment (including, arguably, the UK), but it's not a requirement for civil time. The fact that many countries or part-countries are an hour or more adrift from mean solar time proves that. If you said that people prefer that the middle of the solar night be within a couple of hours of 00:00 local civil time, I might be more ready to agree. But that can be met equally well without leap seconds for several hundred years from now, and then for another several hundred by a one-off adjustment that, as Ian has already pointed out, is trivial to carry out and has been done many times in many countries. 1) What is the cost of leap seconds? A lot of programming, much of it wrong. I'll estimate at 2 milliard pounds per annum. 3) There is an assumption - without benefit of any documentation whatsoever - that timezone adjustments can indeed serve this stated purpose. If this stated purpose is keeping local civil time within 2 or so hours of mean solar time, then it looks pretty obvious to me. If this is obvious (I don't find it such), then it should be easy to write a description of how this would work. (1) Population of area note that sunset is getting earlier and earlier, so that it's now 19:00 in the summer and 14:00 in the winter (substitute other times if you like). (2) Population invoke the local democratic process. (3) Legislation is passed similar to the British Summer Time Act. (4) On the appointed date: (4a) If it's somewhere like India or Arizona adjust their clocks and watches by the value chosen in (3). (4b) If it's somewhere like the EU or California, people do absolutely nothing. a) Please address the northern/southern hemisphere issue. What issue? b) Only a small fraction of the world observes daylight savings, please address what the others might do. See 4a above. c) Please indicate how this addresses the problem of acquiring Universal Time in between adjustments. What problem? I don't need Universal Time, therefore there is no problem. d) And what is the cost of implementing this? Trivial. Currently the zone system is tied worldwide to an underlying mean solar time standard. The notion is to fragment this such that different localities will separately realize whatever synchronization they deem necessary. That is total nonsense. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Straw men
Ian Batten said: Y2K? You do realise that The astronomical community started preparing for Y2K in 1996 and barely had enough time isn't something to be proud of, don't you? We'd _finished_ by 1996, having started the programme in about 1989. Indeed. In 1985 I was sitting in meetings of CSE (remember those?) examiners, pointing out that Y2k was on its way and therefore answers that allowed for 4 digit years should not be penalised. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Bulletin C number 43
Poul-Henning Kamp said: This leapsecond is scheduled on a saturday, if they had used december past it would have been one of the more special fridays in the year, so it may be a concern for minimizing impact on commerce. /me is confused 2011-12-31 was a Saturday. I was there. 2012-06-30 will be a Saturday, though the leap second will happen on the Sunday in my local time zone. 2012-12-31 will be a Monday. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] What is GMT?
Michael Sokolov said: For me GMT has a very simple meaning: it basically means the exact timescale doesn't matter, it can be anything as long as it comes from someone like Rob Seaman and NOT from someone like PHK. Who let Humpty-Dumpty on to this list? -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] China move could call time on GMT
Ian Batten said: Given there's some ambiguity about leap-year rules out into the far future anyway, There is? Both the Papal bull and UK legislation look clear enough to me. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Leap Day: Samoa to skip Dec 30
Zefram said: The western side of the IDL is much more fashionable than the eastern side. The IDL has been gradually shifting eastwards for many years. With the network effect from wanting to have one's timezone close to that of one's geographical neighbours, I wonder if there's actually any stable location for it. Maybe it's going to secularly sweep right around the globe forevermore (or at least until timezones per se go out of fashion). I suspect that we may see the various Polynesian islands, perhaps as far as Gambier or even Pitcairn, dragged across in the way you suggest. But Hawaii and Rapa Nui are going to want to stay on the same day as the rest of their country, and I don't see the Americas being particularly attracted to New Zealand. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Computer Network Time Synchronization, 2nd Ed.
Rob Seaman said: But you did it yourself. Birth certificates list both time and place. Mine doesn't list time, nor do any of those of my family (who were born in two different countries, by the way, so this isn't just a UK thing). -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] No leapseconds on trains
Ian Batten said: This wasn't the timetable. Its main purpose, as I understood it, was to provide a record of where trains were, or where the dispatchers thought they were, in the event of an accident. Hmm, they may well be logging each track circuit transition Track circuits? In manually-signalled USA? The USA had track circuits well before the UK. Read Rolt. I thought it was fairly usual to track circuit at least sections of lines - for example, in remote areas signals were approach-lit to save battery life, so that implies several TCs in rear of the signal. Anyway, the average freight train in the USA is 6500 feet long (ie substantially over a mile) and travels at an average of around 20mph, or at most 30mph. So it takes around two minutes to pass a point. Timing that to a precision of a second seems a excessive. True. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] No leapseconds on trains
Poul-Henning Kamp said: For further reading, I can recommend the ERTMS(2) family of standards, they integrate all trains in a control-domain in a wireless network and does away with red/green lamps. When it works. The trial setup on the Cambrian lines doesn't seem to be going well - it can't cope with two trains requesting authority from the same track section in close succession, which is a problem on a line that divides trains! -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] No leapseconds on trains
Paul J. Ste. Marie said: Hmm. In the UK the working timetable (not the public one) is written to a precision of half a minute. This wasn't the timetable. Its main purpose, as I understood it, was to provide a record of where trains were, or where the dispatchers thought they were, in the event of an accident. Okay. The logged locations weren't stops on the lines. Hmm, they may well be logging each track circuit transition (I belive that SSIs here do that). In which case a second is about the right granularity; TRs normally have a delayed pick of a couple of seconds for safety reasons, and the reporting time from trackside module to interlocking runs on a basic cycle of several hundred milliseconds. So a 1 second error isn't going to faze anyone. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] No leapseconds on trains
Poul-Henning Kamp said: (Unix and ANSI-C format). Doing that, it is immediately obvious to even the causual observer, that the job of the parantheses is to settle any questions with respect to leapseconds by saying Like UNIX, we don't have them. But C does have them. Indeed, C90 allowed two in the same minute! I agree with Paul; it's self-inconsistent. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] What timekeeping system should the Terra Nova settlers use?
Tony Finch said: Another way is to have TAI hours and minutes and seconds, with each day ending with a partial hour. This is the arrangement in Kim Stanley Robinson's Mars trilogy. And the Honor Harrington books, which is where I got it from. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] What timekeeping system should the Terra Nova settlers use?
The length of a Martian solar day is currently about 88775.24409 s (per Wikipedia), yielding an average minute length for a UTC equivalent of 61.6494751 s. On Paleoterra you'll want an average minute length somewhere between 58.0 s and 59.4 s. So on Mars you'll want about 65% of minutes to be 62 seconds long and the rest 61 seconds long. There'll have to be alternation of minutes within each day, which could be mostly according to a regular pattern, That's one way to do it, certainly. Another way is to have TAI hours and minutes and seconds, with each day ending with a partial hour. Digital time displays would have no problem with this, calculators can be used if you actually need to work out how long an interval stretching over midnight was, and analogue clocks and watches become intriguing gadgets (noting it's no more difficult than my radio-controlled clock that moves its hands around to correct the time, or my wristwatch whose analogue stopwatch winds back when I reset it or forwards when I end a pause). -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Leap smear
Rob Seaman said: If you don't believe that civil time is time-of-day where day means synodic day, then assert an alternate definition for what the word day means. I don't believe it. I *know* that a day is the length of time it takes the little hand of the clock to rotate completely twice. Or, more precisely, the specific clock at NPL. Actually, as we've discussed here ad nauseam, where I live the day is de jure the mean solar day at Greenwich and de facto 794243384928000 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] the abbreviation UTC
mike cook said: My argument is not that the lawmans watch is not to any particular accuracy , but that it might be showing some value ( time ) that has no legal existence. Lawyers like that stuff. Judges don't. (Well, it might amuse them briefly, after which you'll get thoroughly and sarcastically squelched.) Time has a legal existence, both de facto and in various bits of legislation. In your example there are three relevant timescales: UTC, GMT, and the time shown by the watch. These differ from each other by some value. The *only* thing the judge will care about is whether the difference is significant to the case. It is likely that the traffic warden's watch is within 4 minutes of UTC, so it is within 5 minutes of GMT. If the restriction is no parking between 0800 and 1830 and the ticket says parked from 1122 to 1435, the judge will be quite happy to convict on the basis that you must have been parked there from 1127 to 1430 legal time. End of case. The *only* time it would matter was if the ticket said parked from 1827 to 1900, when the issue of accuracy would be significant. A good example is with Parisian parking meters. It is written in law that anyone selling anything must accept legally accepted currency . This may be a French thing; there's no such statement in UK law. (There's a weaker requirement about paying debts in cash.) So you can have your parking offence canceled by writing Prefect of police to that effect. Have you actually done this successfully yourself, or is this simply something that a friend claims he was told someone else told him that they know someone who did this? -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Metrologia on time
Tom Van Baak said: If you want to play it safe perhaps NIST could freeze DUT1 in WWV/WWVB at its current value of -0.3 until someone calls to ask if there's a problem. If years go by before anyone has an issue, then that answers the question. Even better, why not make it vary wildly, even on a per-minute basis. That should shake any complaints out in short order. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Get off my lawn!
Ian Batten said: That paper claims that GPS time follows UTC (USNO) modulo one second. I'm trying to think of any meaning of the word modulo, be it from discrete mathematics, HAKMEM or anywhere else, with which that makes sense. Can anyone hazard a guess at the meaning that is intended? Yes. x modulo y means the remainder when x is divided by y. While it's most often used for integers x and y, with y 1, it has a perfectly good meaning for other cases. So angles, even fractional ones, are normally calculated modulo 360 or modulo 2pi. In this case, it's another way of saying that GPS-UTC is an integer. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Far past and far future
Rob Seaman said: So, if the moment of inertia increases by 0.2 parts per million, the angular velocity must decrease by the same amount to keep the angular momentum constant. If this unfortunate occurrence happened in the current day, length of day would thus increase by 0.017 SI-seconds. This would require a leap second six times per year to accommodate. ...and this is *still* within the scope of the current definition of UTC to accommodate - plus a comfy factor of two for monthly Shannon-Nyquist sampling. Um, this is at a time when LOD is about 172800 seconds. That's a leap second *every second*. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Far past and far future
Rob Seaman said: Um, I said if this unfortunate occurrence happened in the current day. Oh, sorry. It is fairly remarkable that the current UTC standard would scale to handle this admittedly unlikely scenario. Or, perhaps, crustal movements are bigger than a few hundred metres (the MoI calculations are much the same, but the density is much greater. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Far past and far future
Rob Seaman said: Almost the definition of a moot point, but if the oceans boil into the atmosphere, how much of a change will that make to the Earth's moment of inertia - and in what direction? Wikipedia says that the current moment of inertia is 8.04e37, which is close enough to the numbers I get by calculating it, so let's go with that. The mass of the hydrosphere is, apparently, 1.4e21. It's all close to the surface, so let's say that the radius is 6.378e6. So the moment of inertia of the oceans is mr^2 = 5.7e34. That's less than 0.1% of the total. If it turns into atmospheric steam at, say, an average height of 1km, that adds a tiny amount to the MoI - about 0.03% of the water's total, or under 0.2 part per million of the earth's total. If it all escapes into space, it reduces the MoI by 0.1% or so. [All quantities are in SI units without prefixes.] -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Far past and far future
Rob Seaman said: Would the earth be slowing down so fast without the moon? There's some tidal coupling in the earth-sun system but isn't it much smaller? Wonderful questions. I'll bet there are lurkers here who could speak authoritatively :-) There is no way that I can speak authoritatively about this. But I took some numbers from the Williams paper that was cited and played with them in a spreadsheet. These suggest that about 90% of the terrestrial rotational angular momentum reappears as lunar orbital angular momentum. On the other hand, I can't see where the rest of it would go - apparently observations show no indication that the Earth's orbit is growing. The tides themselves are only a means to an end mediating the transfer of terrestrial rotational angular momentum to lunar orbital angular momentum. The efficiency of this is presumably an interesting (and perpetually varying) combination of many factors, It's suggested in my reading that the present period has an abnormally high transfer rate because of the present arrangement of the continents and, therefore, the oceanic tides. Certainly the present rate cannot have happened for long periods - projecting back they make the moon collide with the earth about 1 to 2 Gyr ago. Tides are an inverse-cube effect suggesting that the coupling was stronger in past aeons since the Moon was closer. The deceleration ought be decelerating in a smoothed long-term trend. That's not what the numbers appear to show. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Far past and far future
Steve Allen said: Does anyone have figures on how far back or forward I can project based on that figure? What was the length of the day in the time of the dinosaurs? If there's a better reference than Williams somebody please say so. http://www.agu.org/pubs/crossref/2000/1999RG900016.shtml Thanks for this one. It was just the sort of material I was looking for. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Far past and far future
But I took some numbers from the Williams paper that was cited and played with them in a spreadsheet. These suggest that about 90% of the terrestrial rotational angular momentum reappears as lunar orbital angular momentum. On the other hand, I can't see where the rest of it would go - apparently observations show no indication that the Earth's orbit is growing. I've also just realized that the numbers are within the range of experimental error. I get the following angular momenta out of Williams: EarthMoonTotal 2450 My ago74502750034950 900 My ago67302810034830 620 My ago64002840034800 Now58402890034740 That's a total loss of under 1%. Some of the source numbers are +/-3%, and no doubt there are rounding errors in my calculations. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Far past and far future
Tony Finch said: Would the earth be slowing down so fast without the moon? There's some tidal coupling in the earth-sun system but isn't it much smaller? Solar tides are about 40% of lunar ones. But I don't know how that maps into tidal acceleration of orbits. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Far past and far future
Rob Seaman said: But how long term is that? Does anyone have figures on how far back or forward I can project based on that figure? What was the length of the day in the time of the dinosaurs? The abstract to the reference in Steve's reply rather suggests a number of 22 SI-hours at 620 MYA (ymmv). The whole paper suggests: 18.8 hours at 2450 Ma 20.8 hours at 900 Ma 21.9 hours at 620 Ma Converting the paper's numbers into smooth curves for angular momentum and lunar distance and then back-calculating, that projects into the future as: 30 hours at 1000 My 48 hours at 2100 My The latter, allegedly, is when increased solar radiation will boil the oceans and effectively stop tidal coupling. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
[LEAPSECS] Far past and far future
Lunar laser ranging says that the length of day is increasing by about 2.3ms per century in the long term. But how long term is that? Does anyone have figures on how far back or forward I can project based on that figure? What was the length of the day in the time of the dinosaurs? Oh, and to stop me having to reconstruct the formula from first principles, does anyone have the relationship between length of day and distance to the moon? Thanks in advance. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Consensus building 2
Stephen Colebourne said: Local time * definition: local-time - the time-scale local to a region of the Earth * definition: offset - the duration that local-time differs from the locally recognised legal standard time-scale Sorry, that's nonsense. By definition, that offset is always zero, since local-time is always equal to the locally recognized legal standard time-scale. What you mean is the difference between local-time and some global timescale such as UT1, UTC, or TAI. * definition: time-zone - a region of the Earth where local-time is coordinated coordinated with what? Local time in the whole EU (minus those bits in the Americas) is coordinated, but it's not all the same. Try a region of the earth where local time is intended to be the same throughout that region at any time of the year. Note that there are a slew of issues that this still glosses over. For example, the UK and Portugal are currently both in UTx+0100 between certain dates and UTx+ the rest of the year, but in the past they had different changeover dates. Does this make them one time zone or two? [Olsen finesses this; an Olsen timezone is a region of a single country, and the always the same rule only applies from 1970 onwards.] As another example, if one country bases its legal time on UT1 and another on UTC, can they be in the same time zone? * the offset from local-time to TAI-2008 can be calculated given what? And why is this not true for UTC-1972-offset? Or UT1-offset? Humanity - definition: humanity-day - a non-scientific, commonly used term understood by 6bn humans I don't accept that that is a commonly used term. Rather, it's a term you've invented for these discussions, defined by: * a humanity-day is interpreted in line with the rising and setting of the Sun at a single Earth location (and I don't have a problem with that, so long as you're honest about it). -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] What's the point?
Poul-Henning Kamp said: The UK's standard time broadcast, which is funded by the government, contains DUT1 in a format which doesn't permit |DUT1|0.9.Whatever people argue (rightly) about the de facto legal time in the UK being UTC, the de jure legal time is GMT which is taken to be UT1. Where and by who is that taken to be UT1 ? Just about everyone. Since GMT well predates the invention of UTC, it can't be anything other than UT, UT1, or UT2. Just because the additional DUT information is broadcast is no guarantee that any decodes it and uses it. True but irrelevant. And I certainly do not see a DUT offset between NTP servers in the rest of the world and NTP servers in the UK. Because those NTP servers provide UTC-with-leap-second-issues, not UT1, just like the ones in the rest of the world. Curiously enough, NTP is *NOT* the definition of legal time in the UK. You will need to document this claim before anybody will buy it, Which one? That GMT = UTC? That legal time is GMT? and I am quite sure that if you can, a lot of people will be very surprised... Well, as to the latter, the 1978 law says: | Subject to section 3 of the Summer Time Act 1972 (construction of | references to points of time during the period of summer time), whenever an | expression of time occurs in an Act, the time referred to shall, unless it | is otherwise specifically stated, be held to be Greenwich mean time. This is almost certainly a tidying up of older legislation in the same wording, but I don't have quick access to that. The Summer Time Act 1972 says: | 1(1) The time for general purposes in Great Britain shall, during the | period of summer time, be one hour in advance of Greenwich mean time. | (2) The period of summer time for the purposes of this Act is the period | beginning at one o'clock, Greenwich mean time, in the morning of the last | Sunday in March and ending at one o'clock, Greenwich mean time, in the | morning of the last Sunday in October. | | 3(1) Subject to subsection (2) below, wherever any reference to a point | of time occurs in any enactment, Order in Council, order, regulation, | rule, byelaw, deed, notice or other document whatsoever, the time referred | to shall, during the period of summer time, be taken to be the time as | fixed for general purposes by this Act. | (2) Nothing in this Act shall affect the use of Greenwich mean time for | purposes of astronomy, meteorology, or navigation, or affect the | construction of any document mentioning or referring to a point of time in | connection with any of those purposes. The 1954 legislation for Northern Ireland says: | Words in an enactment relating to time and references therein to a point of | time shall be construed as relating or referring to Greenwich mean time, | subject, however, to any statutory provision which may for the time being | provide that, during any specified period or periods, time in Northern | Ireland is to differ from Greenwich mean time. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] What's the point?
Poul-Henning Kamp said: Mean Solar Time = UT1 = GMT: So everybody using NTP and deriving GMT withut applying DUT are in breach of the law ? They're simply getting it wrong. The law doesn't require the use of GMT for everything; it just defines what legal time is. If it came to a lawsuit over the exact time that something happened relative to a statutory boundary, then such an NTP server would not be good evidence. Compare Curtis v March [1858] 3 HN 866. I bet more people would be surprised and in violation, than you will find in compliance... For one thing, all the Rugby receiving radio-controlled clocks do not apply the DUT bits... If those clocks were being sold as GMT clock or UK legal time clock, then the seller would be in breach of the Sale of Goods Act. But I don't believe they are; they're just sold as self-synchronizing to MSF. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] What's the point?
Mark Calabretta said: The speculation on the list is that in the absence of a central authority, local governments will act as their people request when it is staying dark too late and parents can't get their kids to bed with the sun still shining, or have to drive to work in the dark too many days of the year. Yes, it seems a likely response. The underlying assumption is that people expect the Sun to be roughly overhead at noon to within a tolerance of about an hour. I don't believe that's so. I might agree that people expect it to be within about 3 hours, but that's all. Leaping timezones would be tenable if they all leapt at the same time. However, I think we agree that that won't happen. What's the problem with them moving on different dates? Um, beyond the problems we already have because they move on loads of different dates. Currently the main chaotic element of timezones is concerned with the start and end date of DST. The chaos is restricted to two periods, sometime in autumn and spring, and it only amounts to one hour to and fro. FX: laughter. As an example, last year Egypt had two separate sessions of DST. Leaping timezones, each at their own pace, can only add an extra level of chaos, one that will eventually lead to multi-hour offsets that continue to grow over time. Why? Adjacent countries might move from a delta of an hour to zero and then back again, but why would one place move at a different *rate* (i.e. leaps per millenium) to another? In other words, how is this any more complex than Russia deciding not to end DST this year? -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] What's the point?
Ian Batten said: And people routinely live in places where solar time is several hours adrift from civil time --- Brest, France for example is four degrees west of Greenwich, yet in the summer is on UTC+2 --- so at noon civil time it is 0945 solar time. Parts of (mainland) Spain are even further west than that, and there are parts of Alaska where it's 0842 solar time at civil noon. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] one second tolerance
Mark Calabretta said: Not if the timestamps are properly labelled with the timezone, preferably specified as an offset, which distinguishes between DST and non-DST. falls about laughing I was involved in a murder case where the police investigated the wrong person because they hadn't realized the difference between UTC and BST. What makes you think that financial lawyers will think of it. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] one second tolerance
Ian Batten said: Microsoft Exchange meeting invitations say things like GMT: London, Edinburgh, Lisbon, and then contain local timestamps corrected for daylight savings. [...] Yes, I'd forgotten that one. Given that half of my team are now based in Bangalore and the other half in Cambridge, much hilarity ensues from time to time as one or the other turns up at the wrong time for a video conference. I can't wait to see what happens at the end of March. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] one second tolerance
Tony Finch said: As far as I can tell from a brief look at the document, the accurate timestamp requirement applies to trading data, and they don't trade when there is a DST change or when leap seconds occur. Does it say that, or are you guessing? DST changes tend to be outside trading hours, but leap seconds happen at 16:00 local time in California. And is there no out-of-hours trading? -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] one second tolerance
As far as I can tell from a brief look at the document, the accurate timestamp requirement applies to trading data, and they don't trade when there is a DST change or when leap seconds occur. Does it say that, or are you guessing? DST changes tend to be outside trading hours, but leap seconds happen at 16:00 local time in California. And is there no out-of-hours trading? Having scanned the document, it appears to assume 24/7 trading. For example, on page 199 it says that an event at 06:00 on Saturday has to be reported by 08:00 on Tuesday. There's a specific mention of an event at 03:59:59. -- Clive D.W. Feather | If you lie to the compiler, Email: cl...@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
