Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
Ian Batten said: The calendar-change legislation took care of that by moving the end date of the tax year from the traditional quarter-day of March 25th to April 6th. March 25 is, of course, Lady Day. More to the point, it was also New Year's Day in England until 31st December 1751 (which is why 1751, not 1752, was the shortest 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] LEAPSECS Digest, Vol 45, Issue 1
David Grellscheid said: The calendar-change legislation took care of that by moving the end date of the tax year from the traditional quarter-day of March 25th to April 6th. Sadly, there was no Hansard yet to record the moment when the Lords realised they would lose 12 days worth of rent otherwise. Actually, if you read the legislation you can see that it made a careful effort to distinguish between things that happened after a period and things that happened on a named date, with the correct treatment for each. * Courts, councils, elections, and other events that are held on a named date stay on that named date. * Courts, councils, etc. that are held on a date defined relative to Easter follow the new Easter algorithm. * Just about everything else stays on the same natural day as it would otherwise have; in particular, fairs, markets, courts that are normally tied to them, certain specific courts, common land openings and closings, due dates of payments, birthdays, -- 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 45, Issue 1
Tony Finch d...@dotat.at wrote: Oh, do tell, where will you get your GMT reference from? If I have trouble figuring it out myself, I'll just E-mail Rob Seaman and ask him what time it is. Given that his views on the subject as expressed on this list are much closer to mine than, say, PHK's, I would trust his answer better than ITU's. MS ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
On 3 Sep 2010, at 08:44, Michael Sokolov wrote: Tony Finch d...@dotat.at wrote: Oh, do tell, where will you get your GMT reference from? If I have trouble figuring it out myself, I'll just E-mail Rob Seaman and ask him what time it is. Suppose I wish to measure 10 solar seconds from now, forward. I have a clock ticking SI seconds at arbitrarily high precision and resolution. How do I find out how many SI seconds I should count in order to count ten UT1 seconds? Can I determine that value prospectively, or only retrospectively? The reason I ask is that in a mean timescale, it obviously matters which range of time is the basis for the average. I'm not clear if it's the (some period) up to the beginning of the interval, (some period) up to the end of the interval, (some period) up to some other datum or what. In several of these scenarios, it's not obvious how you would determine the conversion between UT1 seconds and SI seconds prospectively. ian ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
Remember to practice safe time transfer. Always use rubber seconds. Stay safe. Warner On Sep 3, 2010, at 1:46 AM, Rob Seaman sea...@noao.edu wrote: And I'd point you to Steve Allen :-) On Sep 3, 2010, at 12:44 AM, Michael Sokolov wrote: Tony Finch d...@dotat.at wrote: Oh, do tell, where will you get your GMT reference from? If I have trouble figuring it out myself, I'll just E-mail Rob Seaman and ask him what time it is. Given that his views on the subject as expressed on this list are much closer to mine than, say, PHK's, I would trust his answer better than ITU's. MS ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
On 3 Sep 2010, at 05:50, Rob Seaman sea...@noao.edu wrote: I was referring to GMT broadly as the astronomical timescale and for all practical purposes de facto the same as UTC. My point is that if you are being precise this is nonsense. GMT in the historic sense of a solar timescale does not exist any more. Your systems cannot be synced to solar GMT in any precise sense. If you are syncing to a solar timescale it will have a different name. If you are syncing to what is now called GMT you are syncing to UTC because they are now in practice exact synonyms. I believe Tony is talking narrowly about the official Greenwich Mean Time, more like http://bit.ly/cWcznJ, although it is pretty clear that the public remains very much synced to GMT, eg, http://bit.ly/aHWJYw Yes well the discourse in the UK about Greenwich's place in the world is pretty delusional. Everyone basically ignores all developments since the mid 1950s: Airy's instrument still determines the prime meridian etc. It's a pity because the truth is a lot more interesting, and if we are to understand time and place properly it's instructive to know why the RGO was abolished and why WGS84 (and for that matter the ordnance survey grid) do not align with the Airy circle. Tony. -- f.anthony.n.finch d...@dotat.at http://dotat.at/ ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
Tony Finch wrote: On 3 Sep 2010, at 01:41, msoko...@ivan.harhan.org (Michael Sokolov) wrote: I very soon will, as soon as I get my rubber time generator working. Oh, do tell, where will you get your GMT reference from? If I were doing it, I would take the DUT1 projections from IERS Bulletin A ftp://maia.usno.navy.mil/ser7/ser7.dat, interpolate between them, and add the resulting DUT1 onto a UTC clock that is synchronised by NTP. At the millisecond level this should provide a satisfactorily smooth approximation of UT1. Of course, it will not reflect any diurnal influences on DUT1, nor any unpredictable rapid changes such as those resulting from earthquakes. There would also necessarily be some discontinuity when switching from one set of projections to the next later-produced set of projections; optionally one could paper over that by slewing gradually between sets of projections, though this would degrade the accuracy of the simulated UT1 frequency. I note that in this endeavour leap seconds in UTC are a slight inconvenience, because they result in discontinuities in DUT1. The clock logic would have to treat these discontinuities specially. It would be slightly easier if Bulletin A supplied UT1-TAI instead of UT1-UTC, and the underlying NTP-synchronised clock supplied TAI instead of UTC. Actually, probably the easiest way to handle the leap second discontinuities is to transform Bulletin A and the NTP clock into this TAI-based form. So it's not really much more inconvenience than the difficulty of getting a clock to tick UTC through a leap second in the first place. -zefram ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
Don't disregard ITU totally here. ITU-T has UTC written into the standards for cross-TelCo billing interfaces/protocols. ...all the implementations of those standards just use unix time. -paul ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
On Fri, 3 Sep 2010, Zefram wrote: Tony Finch wrote: Thanks for the informative explanation, but GMT is not and was not UT1. Picky, picky. OK, let's look at the strictest sense of GMT, taking the Greenwich meridian to be defined by the Royal Observatory, Greenwich, rather than by the ITRF. Specifically, the 1851 meridian defined by Airy's transit circle, adopted as the prime meridian by the International Meridian Conference in 1884. Yet more interesting stuff, thanks again! Another thing to consider is that the last practical astronomical realisation of GMT was carried out at Herstmonceaux not Greenwich, and some errors were introduced when time was transferred from one to the other which is part of the reason for the discrepancy between WGS84 and the Airy circle. Also I understand that GMT included some corrections similar though not identical to UT2 - see also Steve's little history he sent yesterday which said CCIR rec. 374 required time signals to be within 100ms of UT2 between 1963 and 1970. But this is mostly beside the point, which is that there is no organization maintaining and promulgating an official astronomical GMT. You could create a close approximation to an astronomical GMT but it would have no official force. As we have seen there are a lot of intricate details whose necessity people can legitimately disagree about and no way to determine an official consensus. Which is why I say that astronomical GMT doesn't exist. Tony. -- f.anthony.n.finch d...@dotat.at http://dotat.at/ HUMBER THAMES DOVER WIGHT PORTLAND: NORTH BACKING WEST OR NORTHWEST, 5 TO 7, DECREASING 4 OR 5, OCCASIONALLY 6 LATER IN HUMBER AND THAMES. MODERATE OR ROUGH. RAIN THEN FAIR. GOOD. ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
On 3 Sep 2010, at 15:45, p...@2038bug.com wrote: Don't disregard ITU totally here. ITU-T has UTC written into the standards for cross-TelCo billing interfaces/protocols. ...all the implementations of those standards just use unix time. I have a dim memory, based on wrestling with one of the *BSD's NTP implementation in the mid 1990s, that one Unix decided to tick TAI rather than UTC and move leap-seconds into userspace. But it's all very dim... ian ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
Ian Batten wrote: I have a dim memory, based on wrestling with one of the *BSD's NTP implementation in the mid 1990s, that one Unix decided to tick TAI rather than UTC and move leap-seconds into userspace. But it's all very dim... The Olson timezone database has some support for this. It has a listing of leap seconds, which can be included into tzfiles. The zoneinfo-right directory has this version of the tzfiles, whereas the zoneinfo-posix directory has tzfiles that do not mention leap seconds. A wrinkle is the divergence of TAI and UTC prior to 1972, which cannot be properly modelled using leap seconds. I understand that, as a result, the time_t in these systems actually depicts TAI-10s, not TAI. These time_t values coincide with the UTC-based POSIX time_t values for the first half of 1972, and in 2010 the two time_t values differ by 24. I've never seen such a system in operation, though, so I can't confirm that it works this way. -zefram ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
In message: 20100903160248.ga16...@lake.fysh.org Zefram zef...@fysh.org writes: : Ian Batten wrote: : I have a dim memory, based on wrestling with one of the *BSD's NTP : implementation in the mid 1990s, that one Unix decided to tick TAI : rather than UTC and move leap-seconds into userspace. But it's all very : dim... : : The Olson timezone database has some support for this. It has a listing : of leap seconds, which can be included into tzfiles. The zoneinfo-right : directory has this version of the tzfiles, whereas the zoneinfo-posix : directory has tzfiles that do not mention leap seconds. The code that implements these tables just reads them in once at startup, which means programs running longer than 6 months may have have the wrong values... Of course, this is also true if the code is running over a time zone change too... : A wrinkle is the divergence of TAI and UTC prior to 1972, which cannot : be properly modelled using leap seconds. I understand that, as a : result, the time_t in these systems actually depicts TAI-10s, not TAI. : These time_t values coincide with the UTC-based POSIX time_t values for : the first half of 1972, and in 2010 the two time_t values differ by 24. : I've never seen such a system in operation, though, so I can't confirm : that it works this way. The tricky bit is keeping the tables up to date, and convincing the kernel to do the right thing over leap seconds (which in this case is nothing). Also, there are hacks needed for ntp... Such a system can be made to work, but there's a number of hurdles to making it go 100%. Warner ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
Tony Finch wrote: As we have seen there are a lot of intricate details whose necessity people can legitimately disagree about and no way to determine an official consensus. Which is why I say that astronomical GMT doesn't exist. Interesting argument. I disagree with your central point: I don't think an official realisation of GMT is required in order for GMT to meaningfully exist. The details that need to be sorted out are indeed problems in defining GMT, but we don't need an official decision about which definition is the proper one. We can perfectly well decide for ourselves which version of GMT we are interested in, and realise that version of GMT. If interoperability with the historical official realisation is important, we would want to take care to define GMT as closely as possible to the de facto definition behind that realisation. I think ultimately I'm perceiving GMT (or each flavour of GMT) as a Platonic time scale, akin to TT, whereas (despite your choice of terminology) you're perceiving it more as a realisation of a time scale, akin to TT(TAI). The historical official realisation of GMT no longer exists. You see this as meaning that GMT no longer exists, whereas I am open to new realisations of GMT. Making a clear distinction between ideal and realisation smells like modern behaviour; considering the many different meanings of GMT that have already been identified, I would not be surprised at it being irretrievably ambiguous in this respect. Does anyone have relevant historical documentation on the philosophical definition of GMT? -zefram ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
On Fri 2010-09-03T17:45:34 +0100, Zefram hath writ: I don't think an official realisation of GMT is required in order for GMT to meaningfully exist. That means it cannot be a precision time scale, for there is no authority to define a single realization. What the ITU-R is righly tasked to do is to specify a time scale to be used in broadcasts, and that does need to be a precision time scale, so that time scale needs a definition by an authority. Does anyone have relevant historical documentation on the philosophical definition of GMT? GMT is what time it was at the RGO meridian circle as interpolated from moment to moment by the best clock they had. It did not exist in any form prior to 1675. In response to the need to synchronize trans-oceanic telegraphy and as a result of a diplomatic coup hosted by the United States GMT became the basis for worldwide time. The extent to which local civil time needs to be a precision time scale is a different question, and the ITU-R has no direct authority over that. What we're going to see is whether the ITU-R points jurisdictions toward a greater understanding of the need to be careful about specifying time, or whether we are seeing another diplomatic coup in progress. -- Steve Allen s...@ucolick.orgWGS-84 (GPS) UCO/Lick ObservatoryNatural Sciences II, Room 165Lat +36.99855 University of CaliforniaVoice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064http://www.ucolick.org/~sla/ Hgt +250 m ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
On Sep 3, 2010, at 2:18 AM, Tony Finch wrote: If you are syncing to what is now called GMT you are syncing to UTC because they are now in practice exact synonyms. And this is precisely what the ITU is planning to break. This very entrenched assumption will no longer be valid. Reminds me of the lyrics to Istanbul (not Constantinople): UTC was Greenwich Mean Time Now it's UTC, not GMT... Rob ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
On Fri, 3 Sep 2010, Zefram wrote: Tony Finch wrote: As we have seen there are a lot of intricate details whose necessity people can legitimately disagree about and no way to determine an official consensus. Which is why I say that astronomical GMT doesn't exist. Interesting argument. I disagree with your central point: I don't think an official realisation of GMT is required in order for GMT to meaningfully exist. Note that in the above I'm talking about astronomical GMT. There is an official realisation of legal GMT, and it is UTC. If you create a new astronomical timescale it would be wrong to claim it is GMT. GMT(Zefram) is probably OK though :-) Making a clear distinction between ideal and realisation smells like modern behaviour; considering the many different meanings of GMT that have already been identified, I would not be surprised at it being irretrievably ambiguous in this respect. Yes, definitely. I'm stretching when I claim that the practical realities of time in the UK are enough to unambiguously define GMT == UTC (obviously, or we wouldn't be having this discussion). Does anyone have relevant historical documentation on the philosophical definition of GMT? This is brief and sketchy: http://www.nmm.ac.uk/explore/astronomy-and-time/astronomy-facts/history/the-longitude-of-greenwich Tony. -- f.anthony.n.finch d...@dotat.at http://dotat.at/ HUMBER THAMES DOVER WIGHT PORTLAND: NORTH BACKING WEST OR NORTHWEST, 5 TO 7, DECREASING 4 OR 5, OCCASIONALLY 6 LATER IN HUMBER AND THAMES. MODERATE OR ROUGH. RAIN THEN FAIR. GOOD. ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
In message alpine.lsu.2.00.1009031840050.31...@hermes-1.csi.cam.ac.uk, Tony F inch writes: If the ITU change the definition of GMT, and if the British government continues to follow ITU recommendations and to disregard the historical astronomical meaning of GMT, then the equivalence will continue. Just to highlight how laughable the retroimperialist love for GMT is: Which exact meridian are we talking about again ? Are we talking about the meridian Airy drew through his telescope or the one we actually use, about 100m east of his telescope ? Did anybody in England gather an orderly mob around GMT, to protect its imperial virginity, when the WGS84 redefinition of the geodesic origo changed it by five and a half second ? Let me remind you that WGS84 _also_ redefined UTC. Can we please drop this nonsense now ? Or at least queue it, where it belongs, behind the still pending tax-refund for the 12 missing days in september 1752 ? Poul-Henning -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
On 3 Sep 2010, at 22:14, Rob Seaman sea...@noao.edu wrote: Greenwich Mean Time is the Mean Solar Time in Greenwich. Is this its historical astronomical meaning? Or is this its definition? The former, because in current usage it is a synonym for UTC (which I do not regard as an astronomical timescale, though you can reasonably argue otherwise if your required precision is 1 - 10 seconds). Tony. -- f.anthony.n.finch d...@dotat.at http://dotat.at/ ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
Hi Dave, Yes, your post got through. On Sep 2, 2010, at 10:06 AM, Finkleman, Dave wrote: Those that I have access to claim that we can estimate up to about four months in advance with quantified uncertainty. Did you mean four years here? They appear to have been doing just fine with six months since the 1970s :-) would it help overcome some implementation issues if a well conceived warning cycle were implemented as far in advance as such estimates might permit. Yes (as long as the lead time is years, not months). Well conceived is the heart of the issue. The proposal in front of the ITU is poorly conceived on its face whatever one thinks of leap seconds. It cries out for coherent planning and transparency to stakeholders. For just one instance, the proposal is not only to cease leap seconds, but to cease the reporting of DUT1, correct? In the event of the former, does not the latter gain much more importance? A well conceived proposal in whatever policy regime should address the full range of resulting issues. Rob Seaman National Optical Astronomy Observatory ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
On 2 Sep 2010, at 18:37, Rob Seaman wrote: For just one instance, the proposal is not only to cease leap seconds, but to cease the reporting of DUT1 Could you clarify that? DUT1 is surely produced by IERS, who aren't accountable to the ITU, and propagated by (as examples) WWVB and MSF, which are accountable via NIST to the US government and via NPL to the UK government. I assume the other nationally operated time sources have similar governance.I'm not sure how the ITU could stop MSF from reporting DUT1. But if you drop leap seconds in UTC, DUT1 relative to new UTC will rapidly exceed 0.9s, which breaks everything that consumes those signals and, for example, breaks astro-navigation unless somehow the format is fixed to allow for |DUT1|0.9. It would also make the issue of precisely what UK time is a live issue again, because rather than the difference between de jure GMT and de facto UTC being classic DUT1 which is for legal purposes negligible, it would start to get distinctly noticeable as new DUT1 grew larger (assuming a means to propagate it). Why would the UK government accede to this just because the ITU say so, and not just align UTC(NPL) to UTC classic and declare leap seconds itself (based on DUT1 predictions, as today)? It would be interesting to produce a list of countries where legal time is not UTC, to see what the divide would look like. Wikipedia claims Belgium, Canada and Eire: for extra fun, I bet most consumers of time signals in Belgium use DCF77 or TDF, which are clearly in UTC land, rather than MSF. ian ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
In message: 20100902183636.gb13...@ucolick.org Steve Allen s...@ucolick.org writes: : On Thu 2010-09-02T19:26:03 +0100, Ian Batten hath writ: : It would be interesting to produce a list of countries where legal : time is not UTC, to see what the divide would look like. Wikipedia : claims Belgium, Canada and Eire: for extra fun, I bet most consumers : of time signals in Belgium use DCF77 or TDF, which are clearly in UTC : land, rather than MSF. : : IANL, but based on a few documents I've seen : : Canadian standard time is provincial, not federal. : Quebec adopted UTC on 2007-01-01, and the others have not. : : Venezuela standard time is based on the Greenwich meridian, : whatever that means ... : : If that issue were pressed to the courts it would be very interesting : to see the results of the cases in each country especially in the : light of the shifts of the longitude origin during the last 60 years, : the first 3 of which are here : http://www.ucolick.org/~sla/leapsecs/BIHAR1968.JPG I'd wager that UTC, whatever its realization, would likely trump any locally written laws. After all, UTC has been a widely accepted approximation of the local laws that's attained the force of law through repetitive use (how many real-time realizations of UT1 are propagated, in comparison to UTC). So underlying technical changes to UTC may not change that. It would take a long, and complicated, legal argument to show that UT1 is what should be used (even though nobody knows what it is, day to day). Given the current miss-mash of legal rulings around software, I'd guess that this wouldn't be a clear cut ruling that people in this group have suggested. Warner ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
Can't speak for the other Canadian provinces and territories, but the official time for New Brunswick is based on GMT: http://www.gnb.ca/0062/acts/acts/t-06.htm . Of course, they might actually mean UTC but that is not what the act says. -- Richard Langley On 2-Sep-10, at 3:26 PM, Ian Batten wrote: On 2 Sep 2010, at 18:37, Rob Seaman wrote: For just one instance, the proposal is not only to cease leap seconds, but to cease the reporting of DUT1 Could you clarify that? DUT1 is surely produced by IERS, who aren't accountable to the ITU, and propagated by (as examples) WWVB and MSF, which are accountable via NIST to the US government and via NPL to the UK government. I assume the other nationally operated time sources have similar governance.I'm not sure how the ITU could stop MSF from reporting DUT1. But if you drop leap seconds in UTC, DUT1 relative to new UTC will rapidly exceed 0.9s, which breaks everything that consumes those signals and, for example, breaks astro-navigation unless somehow the format is fixed to allow for |DUT1|0.9. It would also make the issue of precisely what UK time is a live issue again, because rather than the difference between de jure GMT and de facto UTC being classic DUT1 which is for legal purposes negligible, it would start to get distinctly noticeable as new DUT1 grew larger (assuming a means to propagate it). Why would the UK government accede to this just because the ITU say so, and not just align UTC(NPL) to UTC classic and declare leap seconds itself (based on DUT1 predictions, as today)? It would be interesting to produce a list of countries where legal time is not UTC, to see what the divide would look like. Wikipedia claims Belgium, Canada and Eire: for extra fun, I bet most consumers of time signals in Belgium use DCF77 or TDF, which are clearly in UTC land, rather than MSF. ian ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
In message cf5fdbc5-0165-4f5a-8c49-65a7fddee...@noao.edu, Rob Seaman writes: Poul-Henning Kamp wrote: ITU-T has UTC written into the standards for cross-TelCo billing interfaces/protocols. So it's literally true: Money makes the world go round Ohh, you bet. Don't remember that railroads was what got us timezones in the first place, and to the right people they were fantastically profitable. If you want to keep leapseconds, all you have to do is come up with the business case. And vice versa. Poul-Henning -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
Poul-Henning Kamp wrote: railroads was what got us timezones in the first place, and to the right people they were fantastically profitable. It was the railroads that were profitable. The timezones were an engineering response forced on the robber barons by real world constraints. Other such real world constraints were rivers and mountain ranges. The Mississippi River and the Rockies weren't amenable to being defined out of existence. That the Earth is round was a similar physical constraint to the gravity that held the steam engines on the tracks. If you want to keep leapseconds, all you have to do is come up with the business case. And vice versa. Precisely. And vice versa. The ITU proposal should be paired with an engineering plan that considers the full range of issues. These include economic issues, but also aspects of physical reality too often neglected by short term business motives. For example, GPS represents a rich (in all senses of the word) cluster of business niches. And yet the proponents of the effort to redefine UTC appear to deride GPS timekeeping even more than leap seconds. Rob E pur si muove ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
In message: 722f0d89-cbfa-423a-9c9e-6d919ded9...@batten.eu.org Ian Batten i...@batten.eu.org writes: : : I'd wager that UTC, whatever its realization, would likely trump any : locally written laws. : : It'll be interesting in the UK : : * There's no doubt that UK legal time is GMT, Interpretation Act 1978, : * S.9 : : * There's no doubt that whatever GMT is, it's solar, and there's no : * doubt that whatever UTC is, it isn't solar and would be even less : * solar without leap seconds, : : * There's no doubt that proposed legislation to change UK legal time to : * UTC failed to be passed in 1997, and an extensive history of the issue : * got read into Hansard. : : You'd have a hell of a job showing UK time was UTC in the face of : that. Do you have references to case law that confirms this interpretation? Citing a literal reading of the current law doesn't prove that the text is the actual law, as interpreted by courts. There are many instances in this country where the literal meaning of the law was interpreted by courts to be more liberal or restricted than the law as written. The national labs that are keepers of the official time have been publishing UTC. I'd t is the de facto standard that everybody is using. Based on that, I suspect someone will make the case that the official time is what people can access as the official time, as opposed to some theoretical time that is extremely difficult to access today. : After all, UTC has been a widely accepted : approximation of the local laws that's attained the force of law : through repetitive use : : That's right, but |DUT1|1 means that for the purposes of integer : arithmetic it's barely more than a rounding error. There's clear, : modern legislation to the contrary. Interesting, but not likely relevant. UTC is a published time everybody can agree on. The technicalities of the legislation may not be relevant if nobody follows them. : (how many real-time realizations of UT1 are : propagated, in comparison to UTC). So underlying technical changes to : UTC may not change that. It would take a long, and complicated, legal : argument to show that UT1 is what should be used : : Not in the UK, see above. The above lacks case law confirmation. Sure, it is what the law says, but that isn't that what it really means. Seriously, when the judge has to choose between a time that people can obtain, and a theoretical one that most people don't have access to, I believe that actual practice will trump theory. These sort of minor corrections to the law, as written, happen all the time. It is impossible for someone today to say, with absolute certainty, what the legal rulings will be in the future. My options here are just that: my guess at the likely outcome. : (even though nobody : knows what it is, day to day). : : That's the paradox, isn't it! Right, but it leads to a legally untenable position. A law that nobody has the practical means of complying with is unenforceable, and is likely to be adjusted by court rulings to be an law that people can comply with. Even before the US officially switched from mean solar time to utc, the us law wasn't mean solar time. It was mean solar time as interpreted by the secretary of commerce, which had for years been interpreting mean solar time to mean UTC... Nobody was propagating anything except UTC... The law said mean solar time, true, but everybody was using and recognizing UTC since that's what NIST was telling everybody was the official time. I don't think this was ever legally tested, however. Warner ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
On 2 Sep 2010, at 20:45, M. Warner Losh wrote: Do you have references to case law that confirms this interpretation? Citing a literal reading of the current law doesn't prove that the text is the actual law, as interpreted by courts. There are many instances in this country where the literal meaning of the law was interpreted by courts to be more liberal or restricted than the law as written. Well, it was considered clear enough that primary legislation was proposed to rectify it: http://www.publications.parliament.uk/pa/ld199798/ldhansrd/vo970611/text/70611-10.htm , and the debate referenced TF460 to state that GMT is UT, not UTC. The debate also outlines leap seconds. But the debate presumes that | DUT1| 0.9s. The debate's worth reading in full to see why the UK House of Lords can be a very sensible body. Not in the UK, see above. The above lacks case law confirmation. Sure, it is what the law says, but that isn't that what it really means. Seriously, when the judge has to choose between a time that people can obtain, and a theoretical one that most people don't have access to, The MSF signal carries UTC(NPL) as the main timecode and DUT1 is provided continuously. So any device that reads MSF can access DUT1. Building a radio clock that displays UT1, or at least one vaguely credible realisation of it, is therefore only a software difference to building one that displays UTC(NPL). Nobody was propagating anything except UTC... But MSF _is_ propagating DUT1. So UT1 is available wherever MSF's writ runs. ian ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
Tony Finch d...@dotat.at wrote: No. You do not run any systems synced to solar GMT. No-one does. I very soon will, as soon as I get my rubber time generator working. MS, who wants to live his life on rubber time (rubber seconds). ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
On 2 Sep 2010 at 12:49, M. Warner Losh wrote: I'd wager that UTC, whatever its realization, would likely trump any locally written laws. After all, UTC has been a widely accepted approximation of the local laws that's attained the force of law through repetitive use They can get away with that now, as the difference between the two is too small to matter except to some highly specialized professions whose issues haven't happened to come before the courts. If the difference is allowed to drift unlimitedly, the conflict would become obvious, and if your side wins, it will be a case of bait and switch, as you've gotten the public to think your scale is close enough for government work to solar time, then you yank the rug from under it. One can never predict, however, which way courts will end up going on that; the Supreme Court in the US in the 1940s found a farmer growing crops to feed to his own animals to be affecting interstate commerce and hence subject to Federal regulation even though none of it ever left the state, and a few years ago they reiterated this decision with regard to Federal bans on medical marijuana grown, sold, and used within a state that allows it by state law. Now they're wrestling with whether or not the Constitution protects the right to gay marriage even though marriage of any sort is never mentioned in the document. (I support it myself, but I'm not sure how good an idea it is to be finding rights out of nowhere in 200- year-old documents.) So it's always a crapshoot. -- == Dan == Dan's Mail Format Site: http://mailformat.dan.info/ Dan's Web Tips: http://webtips.dan.info/ Dan's Domain Site: http://domains.dan.info/ ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
Tony Finch wrote: The fact that it used to be a mean solar timescale is now just etymology. I wrote: I know it to be untrue for systems under my oversight. Tony wrote: No. You do not run any systems synced to solar GMT. No-one does. Perhaps I elided too much context. Tony said: The alternative argument is that GMT (the astronomical timescale) has not been maintained for decades, and all current solar timescales have different more specific names. All official time sources (legal time) in the UK have been synced to UTC for decades. For all practical purposes what we call GMT (the only current use for the term) is now de facto the same as UTC. The fact that it used to be a mean solar timescale is now just etymology. I was referring to GMT broadly as the astronomical timescale and for all practical purposes de facto the same as UTC. I believe Tony is talking narrowly about the official Greenwich Mean Time, more like http://bit.ly/cWcznJ, although it is pretty clear that the public remains very much synced to GMT, eg, http://bit.ly/aHWJYw Rob ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
