Re: [LEAPSECS] presentations from AAS Future of Time sessions
Thanks very much Steve. Great info On 2014-01-11 10:45 PM, Steve Allen wrote: On Sat 2014-01-11T21:43:02 -0800, Brooks Harris hath writ: Any help getting to the bottom of this appreciated. It's history, and it's confused. Measurement techniques were crude and people were not cognizant that there was more than one thing being measured. Measurement techniques are vastly improved and some people understand better, but even the best current knowledge cannot unconfuse the folks in the past or be sure how to interpret their understanding using a modern vocabulary and reference frame. NASA technical report number 70 by Hans D. Preuss of the Department of Geodetic Science at Ohio State University The Determination and Distribution of Precise Time is relevant to read to see how badly confused the situation was in the 1960s http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19670028967_1967028967.pdf NIST has many of the old NBS publications scanned and online at their website, and many of the announcements of rationales and dates when decisions were made to change the radio broadcasts are scattered among those. Their publication with most dense collection of such facts is NBS Monograph 140 which can be found at http://digicoll.manoa.hawaii.edu/techreports/PDF/NBS140.pdf But nobody is going to reset their clocks based on a new understanding of when an epoch was nor what kinds of seconds were being counted. Tabulating historic differences between the values of various time scales is of little relevance to the decision before the ITU-R. How they handle the leap second issue will assert whether humanity has any intent of keeping the meaning of the word day to be based on the rotation of the earth. Yes. Its only relevant in substantiating the standards provance in the interest of completeness. The specific question I was trying to get at was about the 1958 origin of TAI. I had said So that essentially establishes a proleptic TAI timescale from 1958-01-0100:00:00 (TAI) to 1972-01-01T00:00:10 (TAI). And Warner said I don't think TAI is proleptic during that time. I had seen refernce to the fact the 1958 origin was retroactively declared, and this might throw light on why there is a gap in the TIA/UTC tables between 1958 and 1961. So I was hunting for the actual statement in the standards. And I think I've found it in the material you sent. (thanks again, I've been hunting for that for too long.) TIME AND FREQUENCY: Theory and Fundamentals ANNEX l.A DEFINITION OF THE SECOND AND TAI l.A.2. Recommendations of the 5th Session of the Consultative Committee for the Definition of the Second RECOMMENDATION S 4 (1970) Mise en Pratique (Putting into Practice) of International Atomic Time 4. The origin of International Atomic Time is defined in conformance with the recommendations of the International Astronomical Union (13th General Assembly, Prague, 1967) that is, this scale was in approximate agreement with 0 hours UT2 January 1, 1958. So this suggests that the TAI origin was indeed retroactively declared, although it seems there was unofficial agreement about it as far back as 1961. So I'm not sure which part of TAI might be called proleptic, or if its useful to characterize it that way. But the history seems to explain the gap in the TIA/UTC tables between 1958 and 1961. The 1958 origin was put in place when there was enough information and agreement to declare it as such. 1961 is the start of the accumulation of data. -Brooks -- Steve Allen s...@ucolick.orgWGS-84 (GPS) UCO/Lick Observatory--ISB Natural Sciences II, Room 165Lat +36.99855 1156 High StreetVoice: +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 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] presentations from AAS Future of Time sessions
On 2014-01-11 11:47 PM, Poul-Henning Kamp wrote: In message 52d20beb.60...@edlmax.com, Brooks Harris writes: Yes, in my opinion its unfortunate they chose to use the term UTC in that context. They chose UTC because they meant UTC. I have this directly from multiple persons who were involved back then, including Dennis Ritchie who gave me the full sordid details about the early UNIX' requirement of weekly recompiles to update the epoch of the timekeeping. The reason why they didn't cater to leap-seconds ? They hadn't heard about them at the time. And even if they had, they likely wouldn't have bothered, since the PDP-11's kept time based on the mains grid frequency and Ken Thompsons wrist-watch. The trouble starts when Bell Labs starts to commercialize UNIX, polishes the manual pages and goldplates them as System V Interface Definition in 1985, without checking if there are any implicit references to Ken's watch that needed to be resolved. Interestingly, leapseconds appear in network time protocols for the first time in 1985, where previous prototypes does not have support for them, despite the leapseconds in '81, '82 and '83. Later the manual pages also became X/Open, which were fostered by a group of UNIX vendors who wanted BSD networking rather than STREAMS, because the former worked while the latter really didn't, and they didn't notice the bit about leap-seconds either. Eventually it all became dumbed down to POSIX so that Windows NT, VMS and MVS could also qualify, which is were all the crappy APIs (timespec, clock_t etc.) comes from as far as I remember. ...and then the dot-com boom happened, multiplying the cadre of programmers by a factor 1000 and reducing the average knowledge and skill level by the same factor, at the same time as leap-seconds took a break. The rest is (also) history. But time_t has always been UTC, because it was meant to be UTC. Oh, I see what you're saying. Of course - UTC in the historical non-Leap Second period existed, and they intended time_t to reflect it. The trouble now is *modern* UTC has Leap Seconds and these were never adopted. We don't have terms for UTC before 1972-01-01T00:00:00Z and UTC after 1972-01-01T00:00:00Z. -Brooks ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] presentations from AAS Future of Time sessions
On 2014-01-12 12:30 AM, Poul-Henning Kamp wrote: In message 52d251b5.4060...@edlmax.com, Brooks Harris writes: 4. The origin of International Atomic Time is defined in conformance with the recommendations of the International Astronomical Union (13th General Assembly, Prague, 1967) that is, this scale was in approximate agreement with 0 hours UT2 January 1, 1958. I'm not sure if there is a connection, and if there is, which way it might go, but that is also the (theoretical) time of coincidence of all LORAN-C chains. I'm not sure if there is a connection either. When did LORAN-C adopt 1958? ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] presentations from AAS Future of Time sessions
In message 52d257b6.6090...@edlmax.com, Brooks Harris writes: But time_t has always been UTC, because it was meant to be UTC. Oh, I see what you're saying. Of course - UTC in the historical non-Leap Second period existed, and they intended time_t to reflect it. Nice try to twist things to your own viewpoint, but you are wrong. They meant UTC to be UTC. They had absolutely no opinion on leapseconds. Leapseconds, UT, UT1, UT2 or for that matter astronomers or their opinions about time, played absolutely no role in the decision making process. Bell Labs were a telco-sidekick and the telco business used UTC to isolate local timezones and DST issues to a presentation issue. Do I need to remind you that it was telcos caused UTC to be CCITT business in the first place ? Appearantly the only computing person outside timelabs who cared about leapseconds prior to 1985 was Dave Mills. -- 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] presentations from AAS Future of Time sessions
On Sun, 12 Jan 2014 10:58:40 +, Poul-Henning Kamp wrote: In message 52d257b6.6090...@edlmax.com, Brooks Harris writes: But time_t has always been UTC, because it was meant to be UTC. Oh, I see what you're saying. Of course - UTC in the historical non-Leap Second period existed, and they intended time_t to reflect it. Nice try to twist things to your own viewpoint, but you are wrong. They meant UTC to be UTC. They had absolutely no opinion on leapseconds. The original UNIX definition of the Epoch invoked GMT, and POSIX updated this to UTC as it was the obvious successor. The POSIX crowd chose to ignore leap seconds, because one cannot expect an isolated system to know of such things, and it was not necessary to know to meet the requirements of UNIX/POSIX time, chiefly file modification timestamps to ensure (to within one second) causal time ordering. One-second resolution was fine enough to ensure causal order when the policy was adopted, but this fell apart in the 1980s. Leapseconds, UT, UT1, UT2 or for that matter astronomers or their opinions about time, played absolutely no role in the decision making process. GMT is now (unofficially?) deemed to be UT1. In practice, for probably the majority of systems, the time source is the user's wristwatch. Bell Labs were a telco-sidekick and the telco business used UTC to isolate local timezones and DST issues to a presentation issue. Do I need to remind you that it was telcos caused UTC to be CCITT business in the first place ? Apparantly the only computing person outside timelabs who cared about leapseconds prior to 1985 was Dave Mills. Could be. Joe Gwinn ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] presentations from AAS Future of Time sessions
On Sun 2014-01-12T00:26:29 -0800, Brooks Harris hath writ: I had seen refernce to the fact the 1958 origin was retroactively declared, and this might throw light on why there is a gap in the TIA/UTC tables between 1958 and 1961. So I was hunting for the actual statement in the standards. There was nothing that could be called UTC before several months into the year 1960. US and UK agencies had agreed to coordinate in 1959 August, but buried in those old NBS publications is an acknowledgement that they did not get that working until sometime in 1960. Until that date in 1960 all available time scales looked like the plot at the bottom of http://www.ucolick.org/~sla/leapsecs/amsci.html where that depicts NBS only. USNO was different. UK was different. Every other broadcast in the world was different. It was during 1960 that BIH accepted the responsibility for doing the coordination, and they started doing it as of 1961. This is evident in Guinot's 2000 memoire and in the contemporary proceedings of the IAU. Also note in Guinot's memoire that the BIH did not start combining the various different sources of AT into an atomic time scale with unified epoch until 1961. (If I'm not mistaken that new responsibility for tracking atomic time was what prompted BIH to hire Guinot.) Therefore BIH has nothing to say about UTC before 1961. The only way to proclaim a difference of AT and UT before 1961 is to adopt the clocks of a single agency or to go back through all the numbers gathered by the BIH and try to reconstruct what that difference might have been. Doing that sort of thing is rare and often only accomplished as part of somebody's PhD thesis or academic research. The task delegated to time service bureaus is to provide the best value of time now, not to try to compensate for inadequacies of data from long ago. Even after 1961 the USNO and NBS were not attempting to provide the coordinated time scale as specified on paper by the BIH. In NBS140 there are several documents noting that it was not until 1968-10-01 that USNO and NBS started making adjustments so that they would agree with each other, and not until two months later that NBS began to acknowledge that they were providing UTC according to the BIH. -- Steve Allen s...@ucolick.orgWGS-84 (GPS) UCO/Lick Observatory--ISB Natural Sciences II, Room 165Lat +36.99855 1156 High StreetVoice: +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] presentations from AAS Future of Time sessions
In message 52d2e6f5.2030...@edlmax.com, Brooks Harris writes: I think I understand you. You are saying that UTC as a term for the I'm saying that UTC is Universal Time Coordinated, such as defined and used by telcos for a decade by the time UNIX was written. What was inside UTC didn't mater to them, UTC was the accepted international timescale and they used it as such. -- 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] presentations from AAS Future of Time sessions
On 2014-01-12 11:33 AM, Poul-Henning Kamp wrote: In message 52d2e6f5.2030...@edlmax.com, Brooks Harris writes: I think I understand you. You are saying that UTC as a term for the I'm saying that UTC is Universal Time Coordinated, such as defined and used by telcos for a decade by the time UNIX was written. What was inside UTC didn't mater to them, UTC was the accepted international timescale and they used it as such. Oh, I see - the telcos. How do they define it? Is there a standard or guideline they use, or is it just common practice? ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] presentations from AAS Future of Time sessions
On 01/12/2014 02:47 AM, Poul-Henning Kamp wrote: In message 52d20beb.60...@edlmax.com, Brooks Harris writes: Yes, in my opinion its unfortunate they chose to use the term UTC in that context. They chose UTC because they meant UTC. I have this directly from multiple persons who were involved back then, including Dennis Ritchie who gave me the full sordid details about the early UNIX' requirement of weekly recompiles to update the epoch of the timekeeping. If they chose UTC because they meant UTC, then why do the man pages refer not to UTC, but to GMT? http://cm.bell-labs.com/7thEdMan/vol1/man2.bun It sounds like you are rewriting history. ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] presentations from AAS Future of Time sessions
In message 52d2fe51.40...@cox.net, Greg Hennessy writes: On 01/12/2014 02:47 AM, Poul-Henning Kamp wrote: In message 52d20beb.60...@edlmax.com, Brooks Harris writes: Yes, in my opinion its unfortunate they chose to use the term UTC in that context. They chose UTC because they meant UTC. I have this directly from multiple persons who were involved back then, including Dennis Ritchie who gave me the full sordid details about the early UNIX' requirement of weekly recompiles to update the epoch of the timekeeping. If they chose UTC because they meant UTC, then why do the man pages refer not to UTC, but to GMT? http://cm.bell-labs.com/7thEdMan/vol1/man2.bun Dennis specifically said UTC to me. Not that it makes any difference, GMT and UTC were considered the same thing until all this talk about dropping leapseconds started. -- 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] presentations from AAS Future of Time sessions
On Jan 12, 2014, at 2:01 AM, Brooks Harris wrote: I'm not sure if there is a connection either. When did LORAN-C adopt 1958? I can't answer definitively on when, but can point the way to what I know. LORAN-C is defined by COMDTINST M16562.4A. Quoting from chapter 2: This epoch is from 0 hr, 0 min, 0 sec , 1 January 1958. The expected Times-of-Coincidence (TOC) of master station's transmissions with the UTC second are publish in the Times of Coincidence, Null Ephemeris Tables, Section 9 developed by and available from USNO. The difference between the time of the master's transmission with respect to UTC is also published by the USNO in the Series 4 and Series 100 Bulletins. USNO Time Service Information Letter of 15 August 1973, provides guidelines for making time measurements. (from http://navcen.uscg.gov/pdf/loran/sigSpec/chapt2c.pdf) so that puts at sometime before 1973 :). Digging more, we see Series 4 and Series 100 Bulletins from USNO. Or at least references to them (I thought I'd seen them online at USNO but can't find them now). We have a 1983 publication at http://tycho.usno.navy.mil/ptti/1983papers/Vol%2015_05.pdf that states: Prior to the 1970s, data collected by the Observatory were all logged manually and goes on to say that initially only locally monitored time pulses from Loran-C... were available. And talks about 10 years prior (approx 1973) the decision was made to automate collection of this data. It also talks about until recently (1983), the only dissemination of this data was US Mail. But it doesn't tell of when the manual collection of data started, but implies the automated collection started in 1973, give or take a year. Digging into the PTTI archives, we find an article on LORAN-C time keeping that has a good history of LORAN-C starting in 1957, and the transfer of LORAN-C to the USCG in 1958 (see page 79 (page 90 in the pdf) and following). It also talks about how measurements were gathered from 1955 to 1958 that ultimately lead to the standard second definition during LORAN-C development. http://www.dtic.mil/dtic/tr/fulltext/u2/a280955.pdf Perhaps these documents will prove useful in working out TAI's origin, but it seems that LORAN-C started in 1958, and so did TAI time's EPOCH, so there's a strong inference to be made at the connection between the two... In fact, I wish I'd known of this publication sooner, since I worked on the retooling of the LORAN-C timing system in the early 2000's and I love historical stuff like this. I don't know if other PTTI publications are online, but intensive google searching for them might prove fruitful as well. http://tycho.usno.navy.mil/ptti/ looks to contain at least a summary of each of the conferences. It is only intermittently responding to me at the moment. Others might have better luck trolling through there to find additional references that may have somehow escaped the watchful eye of Steve Allen... Warner ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] presentations from AAS Future of Time sessions
On Jan 12, 2014, at 4:01 AM, Poul-Henning Kamp wrote: In message 52d259db.4000...@edlmax.com, Brooks Harris writes: I'm not sure if there is a connection, and if there is, which way it might go, but that is also the (theoretical) time of coincidence of all LORAN-C chains. I'm not sure if there is a connection either. When did LORAN-C adopt 1958? They didn't adopt it, they chose it as a design value. Not sure when. I'm guessing 1958 when they began operations See other mail. Warner ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] presentations from AAS Future of Time sessions
On Sun, 12 Jan 2014 15:42:57 -0500, Greg Hennessy wrote: On 01/12/2014 02:47 AM, Poul-Henning Kamp wrote: In message 52d20beb.60...@edlmax.com, Brooks Harris writes: Yes, in my opinion its unfortunate they chose to use the term UTC in that context. They chose UTC because they meant UTC. I have this directly from multiple persons who were involved back then, including Dennis Ritchie who gave me the full sordid details about the early UNIX' requirement of weekly recompiles to update the epoch of the timekeeping. If they chose UTC because they meant UTC, then why do the man pages refer not to UTC, but to GMT? http://cm.bell-labs.com/7thEdMan/vol1/man2.bun It sounds like you are rewriting history. No, he isn't. In the UNIX before POSIX, it was GMT. When the first POSIX standard was developed, GMT had been deprecated in favor of UTC, so POSIX changed to UTC. Joe Gwinn ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] presentations from AAS Future of Time sessions
Joseph Gwinn joegw...@comcast.net wrote: In the UNIX before POSIX, it was GMT. Your use of the past tense is incorrect. In non-POSIX UNIX, it (the system time definition) *is* GMT, present tense. See my previous post. VLR, SF ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] presentations from AAS Future of Time sessions
On Sun, 12 Jan 2014 22:18:41 GMT, Michael Spacefalcon wrote: Joseph Gwinn joegw...@comcast.net wrote: In the UNIX before POSIX, it was GMT. Your use of the past tense is incorrect. In non-POSIX UNIX, it (the system time definition) *is* GMT, present tense. See my previous post. Well, yes, but I guess it's a bit of hair splitting. The UNIX docs may well still say GMT, but I bet what they really use is UTC, as that's what's distributed. Getting true GMT (~UT1) is a bit more work that would seem necessary for 99.999% of users. Joe Gwinn ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] presentations from AAS Future of Time sessions
On 01/12/2014 05:12 PM, Warner Losh wrote: GMT and UTC were used interchangeably well into the 1990s, especially in publication not subject to peer review of subject experts... People still use them interchangeably TODAY, however the people doing so are incorrect. We can't agree on how to solve the problems if we can't agree on the history of the past. time_t was devised to correspond to a GMT worldview. It worked fine for most purposes in the late 70's. It works less fine in 2014. Pretending that time_t was MEANT to represent UTC isn't intellectually honest in my opinion, and I'll object when I see it presented as such. ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] presentations from AAS Future of Time sessions
On 01/12/2014 05:14 PM, Joseph Gwinn wrote: It sounds like you are rewriting history. No, he isn't. In the UNIX before POSIX, it was GMT. When the first POSIX standard was developed, GMT had been deprecated in favor of UTC, so POSIX changed to UTC. POSIX changed to calling something without leapseconds by a name that means leap seconds. POSIX started calling a tail a leg, and lots of people are trying to argue that calling the tail a leg makes it a leg. I continue to disagree. It is now 2014. The next time the 'drop the leap seconds' will face a vote is sometime in 2015. The current status is that leap seconds exist, no matter how pesky some people find them. If the votes do not exist to change the status the quo will continue. Does anyone want to offer an estimate of when a method of dealing with leap seconds might be standardized? ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] presentations from AAS Future of Time sessions
On 01/12/2014 06:12 PM, Joseph Gwinn wrote: Getting true GMT (~UT1) is a bit more work that would seem necessary for 99.999% of users. Well, 99.999 percent of users don't want or need a PL/1 compiler, but I don't think that is a good reason for saying that they can't have one. Likewise, while getting GMT (even though GMT doesn't exist anymore) or UT1 or proper treatment of leap seconds isn't necessary for 99.999 percent of users, I don't see that as a reason for saying they can't have it. ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] presentations from AAS Future of Time sessions
On Sun 2014-01-12T11:46:16 -0800, Brooks Harris hath writ: So it appears the reference to the International Astronomical Union (13th General Assembly, Prague, 1967) is where the recommendations from BIH come to the statement in l.A.2. Recommendations of the 5th Session of the Consultative Committee for the Definition of the Second RECOMMENDATION S 4 (1970) 4. The origin of International Atomic Time is defined in conformance with the recommendations of the International Astronomical Union (13th General Assembly, Prague, 1967) that is, this scale was in approximate agreement with 0 hours UT2 January 1, 1958. So the 1958 origin was made *official* by this Recommendation. Is that your understanding? I am not sure what official means in the context of recommendations by one body which can be ignored by another body. It is a statement by the CCDS produced under direction of the CIPM which is an extreme shorthand for saying that they believed that the atomic time scale being maintained by the BIH was based on that 1959 agreement that everyone would reset their atomic time scales to epoch 1958-01-01, and that the CCDS believed the BIH had done an adequate job at that task, and the CCDS wanted the next-step-farther-removed-from-the-technical-details delegates of the CIPM to communicate the same thing up to the next-step-up... delegates of the 14th CGPM so that they would officially approve the inception and ongoing maintenance of TAI. In this case the recommendation happens to agree with what IAU comms 4 and 31 had said in resolutions 4 and 5 on page 182 at http://adsabs.harvard.edu/abs/1968IAUTB..13..178S so everybody was happy. But in the same 1967 IAU GA were also resolutions 1 and 2 by comms 4 and 31 (in that same document, but note that there are typos in the enumeration and pagination) which were considered important enough that the entire GA approved them as resolutions 5 and 6 seen on page 41 at http://adsabs.harvard.edu/abs/1968IAUTB..13...41. and the CGPM utterly ignored resolution 5b, so not everyone was happy. I find that the last point at which everyone was in agreement about what the meaning of things were was the 1964 IAU GA discussion in http://adsabs.harvard.edu/abs/1966IAUTB..12..304M which was written by none less than astronomer W. Markowitz, radio-timekeeper H.M. Smith, and physicist L. Essen which was included in the resolutions (see page 16) http://www.iau.org/static/resolutions/IAU1964_French.pdf By the time of the 1967 IAU meeting the statements by various folks who reported the situation in the CCIR and the BIPM seemed to be using imprecise paraphrases of what had been recorded in the proceedings of those other agencies. The documents from the different agencies use different terminology when describing what they must have meant to be the same thing. That left room for paper consensus without actual agreement on the mechanisms. Up until 1970 all of the CCIR recommendations about radio broadcast time scales were basically descriptions of the existing best practices. Recommendation 460 became prescriptive of a change which had not been implemented by anyone, and its prescription contained no instructions about the details of accomplishing the change. The CCIR working party rushed to come up with in interim implementation document before the 1972 deadline. During the next decade the CCIR rejoiced as they saw 460 get adopted by the IAU, the CGPM, the WARC, the CCITT, the governments of France and Germany. Nobody seems to have stopped to ask just how exactly those leap seconds were supposed to be communicated nor handled by systems that could not interpret a telegram from the BIH. -- Steve Allen s...@ucolick.orgWGS-84 (GPS) UCO/Lick Observatory--ISB Natural Sciences II, Room 165Lat +36.99855 1156 High StreetVoice: +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] presentations from AAS Future of Time sessions
Joseph Gwinn joegw...@comcast.net wrote: Well, yes, but I guess it's a bit of hair splitting. The UNIX docs may well still say GMT, but I bet what they really use is UTC, as that's what's distributed. Using UTC as a *realisation* of GMT is acceptable only for as long as UTC remains a *good faith* approximation to GMT. If a decision is made to redefine UTC in such a way that it ceases to be a good faith approximation to GMT, then I will be legally required by the laws of the Micronation of Falconia to stop using UTC the very same day that decision is made. It has nothing to do with any specific numeric bound on DUT1, it has to do with the moral/legal concept of *good faith*. Even if it takes 20 years for UTC to diverge too far from GMT after a deleterious redefinition decision is made, I will not have a luxury of waiting 20 years before doing something about it: I will have to make a complete disconnect from UTC (install firewall rules blocking all major NTP servers that serve UTC, etc) *the very same day* the deleterious decision is made, as that is the day when UTC will legally stop being a good faith approximation to GMT. Building and deploying an alternative non-UTC realisation of GMT will surely be quite expensive, so lawsuits to recover those costs should definitely be expected. Mr. Poul-Henning Kamp will most certainly be among the defendants. VLR, SF ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] presentations from AAS Future of Time sessions
In message 52d2f909.9080...@edlmax.com, Brooks Harris writes: I'm saying that UTC is Universal Time Coordinated, such as defined and used by telcos for a decade by the time UNIX was written. What was inside UTC didn't mater to them, UTC was the accepted international timescale and they used it as such. Oh, I see - the telcos. How do they define it? Is there a standard or guideline they use, or is it just common practice? The main reason CCITT got into UTC standardisation, was to make it possible to precisely schedule and bill international tele-traffic. -- 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] presentations from AAS Future of Time sessions
On 12 Jan, 2014, at 15:42 , Greg Hennessy greg.henne...@cox.net wrote: On 01/12/2014 02:47 AM, Poul-Henning Kamp wrote: In message 52d20beb.60...@edlmax.com, Brooks Harris writes: Yes, in my opinion its unfortunate they chose to use the term UTC in that context. They chose UTC because they meant UTC. I have this directly from multiple persons who were involved back then, including Dennis Ritchie who gave me the full sordid details about the early UNIX' requirement of weekly recompiles to update the epoch of the timekeeping. If they chose UTC because they meant UTC, then why do the man pages refer not to UTC, but to GMT? http://cm.bell-labs.com/7thEdMan/vol1/man2.bun It sounds like you are rewriting history. I don't think the fact that they called it GMT at that point tells you anything since referring to UTC as GMT was pretty common in the US at the time. Even the NBS did it. WWV voice announcements referred to the time being transmitted as GMT from when they stopped announcing MST until 1974 even though the time was very definitely UTC by then (including the DUT1 advertisements). This site https://soundcloud.com/shortwavemusic/sets/at-the-tone-a-little-history/ has a recording of the last announcement calling it GMT and the first calling it UTC; it sounds like DUT1 was 0.3 seconds. The previous recording is the announcement of the change and indicates that the time they'd been calling GMT was in fact UTC. If the NBS's radio service was calling UTC GMT then it shouldn't be surprising that computer programmer contemporaries might do that too. The note that goes along with the recording says that they made the change because of CCIR complaints. Dennis Ferguson ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] presentations from AAS Future of Time sessions
On 12/01/14 09:26, Brooks Harris wrote: Thanks very much Steve. Great info On 2014-01-11 10:45 PM, Steve Allen wrote: On Sat 2014-01-11T21:43:02 -0800, Brooks Harris hath writ: Any help getting to the bottom of this appreciated. It's history, and it's confused. Measurement techniques were crude and people were not cognizant that there was more than one thing being measured. Measurement techniques are vastly improved and some people understand better, but even the best current knowledge cannot unconfuse the folks in the past or be sure how to interpret their understanding using a modern vocabulary and reference frame. NASA technical report number 70 by Hans D. Preuss of the Department of Geodetic Science at Ohio State University The Determination and Distribution of Precise Time is relevant to read to see how badly confused the situation was in the 1960s http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19670028967_1967028967.pdf NIST has many of the old NBS publications scanned and online at their website, and many of the announcements of rationales and dates when decisions were made to change the radio broadcasts are scattered among those. Their publication with most dense collection of such facts is NBS Monograph 140 which can be found at http://digicoll.manoa.hawaii.edu/techreports/PDF/NBS140.pdf But nobody is going to reset their clocks based on a new understanding of when an epoch was nor what kinds of seconds were being counted. Tabulating historic differences between the values of various time scales is of little relevance to the decision before the ITU-R. How they handle the leap second issue will assert whether humanity has any intent of keeping the meaning of the word day to be based on the rotation of the earth. Yes. Its only relevant in substantiating the standards provance in the interest of completeness. The specific question I was trying to get at was about the 1958 origin of TAI. I had said So that essentially establishes a proleptic TAI timescale from 1958-01-0100:00:00 (TAI) to 1972-01-01T00:00:10 (TAI). And Warner said I don't think TAI is proleptic during that time. I had seen refernce to the fact the 1958 origin was retroactively declared, and this might throw light on why there is a gap in the TIA/UTC tables between 1958 and 1961. So I was hunting for the actual statement in the standards. And I think I've found it in the material you sent. (thanks again, I've been hunting for that for too long.) TIME AND FREQUENCY: Theory and Fundamentals ANNEX l.A DEFINITION OF THE SECOND AND TAI l.A.2. Recommendations of the 5th Session of the Consultative Committee for the Definition of the Second RECOMMENDATION S 4 (1970) Mise en Pratique (Putting into Practice) of International Atomic Time 4. The origin of International Atomic Time is defined in conformance with the recommendations of the International Astronomical Union (13th General Assembly, Prague, 1967) that is, this scale was in approximate agreement with 0 hours UT2 January 1, 1958. So this suggests that the TAI origin was indeed retroactively declared, although it seems there was unofficial agreement about it as far back as 1961. So I'm not sure which part of TAI might be called proleptic, or if its useful to characterize it that way. But the history seems to explain the gap in the TIA/UTC tables between 1958 and 1961. The 1958 origin was put in place when there was enough information and agreement to declare it as such. 1961 is the start of the accumulation of data. You have to realize that experiments on atomic timescale goes back to 1956, so as they figured things out they sketched out how it needs to work. Only then you can formulate definitions and even then it takes time before formalization can be done as it becomes clear. It's ongoing research. So, it's not proleptic, but rather formalization of informal agreement. I've too found the lack of early formal definitions disturbing until realizing as they where inventing it as they go. Once you know that the formalization just came afterhand, then helps to see the cause-action pattern better and the formalization does operate in the span. I have not found any TAI-UT1 data, but it is probably hidden in some obscurity considering the labs being involved. Would be a nice find to make. Cheers, Magnus ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
