Re: two world clocks AND Time after Time
In message [EMAIL PROTECTED], Clive D.W. Feather writes: Poul-Henning Kamp said: [That is, if the equinox was actually on March 9th, would anyone outside the astronomical community notice?] I doubt it. I'm not so certain about the summer and winter solstice however. here in the nordic countries were're quite emotionally attached to those. Hmm, that's because you actually get midnight sun and midday night (or approximations like the White Nights). That is probably how a foreigner would say it. We would tend to say it's because it's so bloddy dark all winter :-) But given that these dates move a day or two each year anyway because of leap year effects, you wouldn't notice the drift without being told. More superstition is attached to those, so people might not take it (as) lightly. And talking about superstition... The NeoPagans will demand that we rotate Stone Henge to match. The UFOlogist will insist that we turn the Great Pyramid accordingly. And just wait until the astrologers find out... Poul-Henning -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.
Re: two world clocks AND Time after Time
On Tue 2005-01-25T09:57:46 +, Clive D.W. Feather hath writ: I think you're out by a factor of 10. Would the Man On The Clapham Omnibus be able to identify the solstice or equinox to within 14 days? Other than knowing the conventional dates? [That is, if the equinox was actually on March 9th, would anyone outside the astronomical community notice?] The answer is in Duncan Steel's book Marking Time http://www.wiley.com/WileyCDA/WileyTitle/productCd-0471298271.html The answer is yes, and it is evident in the orientation of churches in England built before and after the English calendar reform in 1752. Churches were built oriented to sunrise on their saint's day. In 1752 the calendar shifted, and sunrise shifted. Additions made to pre-reform churches were oriented to sunrise on the new saint's day. The result was crooked churches. Steel counts 81 such churches within Oxfordshire alone. -- Steve Allen UCO/Lick Observatory Santa Cruz, CA 95064 [EMAIL PROTECTED] Voice: +1 831 459 3046 http://www.ucolick.org/~sla PGP: 1024/E46978C5 F6 78 D1 10 62 94 8F 2E49 89 0E FE 26 B4 14 93
Re: Time after Time
John Cowan wrote on 2005-01-23 18:37 UTC: Markus Kuhn scripsit: UTC currently certainly has *no* two 1-h leaps every year. There seems to be persistent confusion on what is meant by the term leap hour. Why? I understand it as a secular change to the various LCT offsets, made either all at once (on 1 Jan 2600, say) or on an ad-lib basis. No. A UTC leap hour is an inserted 60-minute repeat segment in the UTC time scale, which starts by jumping back on the UTC time scale by one hour. This has been proposed by BIPM in Torino to be done for the first time to UTC in about 2600, instead of doing the about 1800 leap seconds that would be necessary under the current |UTC - UT1| 900 ms until then. The proposed UTC leap hour simply means that the definition of UTC is relaxed to (something like) |UTC - UT1| 59 min, and the size of the adjustment leap is increased accrodingly from 1 s to 3600 s. Local civilian times are of no convern to ITU, as they are entirely the responsibility of numerous national/regional arrangements. You seem to be using it in the sense of a 1h secular change to universal time (lower-case generic reference is intentional). I can't understand what could be ambiguous here. A leap hour means to turn a clock forward or backward by an hour. We have done it twice a year in many LCTs. The BIPM suggested in Torino that we should do it every couple of hundred years to UTC as well, which would become permissible by going from the rule |UTC - UT1| 900 ms to a relaxed rule such as |UTC - UT1| 59 min. The term leap hour does in no way imply what time zone/scale we are talking about, and in this context we are talking mostly about UTC. [How a UTC leap hour would affect LCTs is up the maintainers of the these LCTs. Since the LTCs currently in use have their leap hours on many different days of the year, a UTC leap hour would mean that at least some LCTs would have three leap hours in that year. This could only be avoided if all LCTs would agree to do their DST leaps simultaneously with the UTC leap.] In summary: There are basically three proposals on the table: a) Keep UTC as it is (|UTC - UT1| 900 ms) and just make TAI more widely available in time signal broadcasts b) Move from frequent UTC leap seconds to far less frequent UTC leap hours, by relaxing the UTC-UT1 tolerance (e.g., |UTC - UT1| 59 min) c) Remove any future leap from UTC, such that UTC becomes TAI plus a fixed constant (i.e., |UTC - UT1| becomes unbounded and will start to grow quadratically). In this scenario, LCTs would have to change their UTC offset every few hundred years, to avoid day becoming night in LCTs. My views: a) is perfectly fine (perhaps not ideal, but certainly workable) b) is utterly unrealistic and therefore simply a dishonest proposal (UTC is so popular today in computing primarily because it is *free* of leap hours) c) I could live with that one, but what worries me is that it will create a long-term mess in a few millenia, when |UTC-LCT| 1 day. I am annoyed that this long-term mess and solutions around it are not even being discussed. (My hope would have rested on resolving the |UTC-LCT| 1 day problem by inserting leap days into the LCTs every few thousand years as necessary, to keep |UTC-LCT| 36 hours this way, and that these leap days in LCTs could perhaps be the same that may be necessary anyway every few millenia to fix the remaining Easter drift in the Gregorian calendar: http://www.mail-archive.com/leapsecs@rom.usno.navy.mil/msg00206.html ) Markus -- Markus Kuhn, Computer Lab, Univ of Cambridge, GB http://www.cl.cam.ac.uk/~mgk25/ | __oo_O..O_oo__
Re: two world clocks AND Time after Time
In message [EMAIL PROTECTED], Tom Van Baak writes: Another observation is that our local newspaper always prints Sun and Moon rise and set times. But not time of noon. Why is this? Maybe it's just our paper (noon implies sun and we don't see much of it here in Seattle). Why is the instant of sunrise or sunset of popular value while the high point of noon isn't. What does this suggest about the risk of allowing noon to wander an hour over the span of 1000 years? Several countries have codified sunrise and sunset as when traffic needs to light up. In Denmark while cars and motorbikes are lit up at all times, bicycles and horses must be lit up from sunset to sunrise. There are similar rules for vessels on water I belive. Month is entirely conventional in its meaning. Year is entirely conventional in its meaning. So soon day will be entirely conventional in its meaning. Can you explain this more? I can see how Month would be conventional, or even entirely conventional but are year and day also such extreme cases? The Year represents when the constellations repeat their performance, but the precision of this is wrecked by the leap-years, so it is only conventional these days. It seems to me the popular understanding of a year is accurate to +/-1 day. And the popular understanding of noon is accurate to +/- 1 hour or two. Does that make them entirely conventional? Seen from an astronomical point of view: yes, you can't point your telescope with it. The trick will be to educate the general public that 12:00 means slightly less about where the sun is in longitude than the Gregorian Sure, but it seems to me - regardless of the timezone, regardless of daylight saving time, regardless of the season, regardless of latitude, to the general public 12:00 means lunchtime (or their VCR got unplugged). The sun doesn't have much say about it. Fully agreed. I would even venture to claim that a lot of todays teenagers are only mildly aware of the noon -- more light outside connection :-) -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.
Re: two world clocks AND Time after Time
On Mon 2005-01-24T00:50:10 -0800, Tom Van Baak hath writ: Isn't knowing when noon is already a specialist operation? I mean, most people could tell you when noon is to within an hour or two or three, but finer than that requires a far amount of daily mental calculation, no? Noon has long required a calendar, an almanac, a longitude, and the ability to perform addition and subtraction. This has long been something that could be presumed within the abilities of any locality big enough to call itself a town. The tasks of business, payroll, and banking demand that much. Sunrise and sunset have required haversines. That's why the newspapers publish them. Trigonometry was not required for simple civil life. -- Steve Allen UCO/Lick Observatory Santa Cruz, CA 95064 [EMAIL PROTECTED] Voice: +1 831 459 3046 http://www.ucolick.org/~sla PGP: 1024/E46978C5 F6 78 D1 10 62 94 8F 2E49 89 0E FE 26 B4 14 93
Re: Time after Time
In message [EMAIL PROTECTED], Markus Kuhn writes: You surely must have seen my detailed UTS proposal for how UTC leap seconds should be handled trivially and safely by the overwhelming majority of computer applications, without any special considerations whatsoever by normal application programmers: http://www.cl.cam.ac.uk/~mgk25/time/leap/utc-torino-slides.pdf http://www.cl.cam.ac.uk/~mgk25/uts.txt Markus, that's all very nice and cute, but it is a grusome hack and should not be propagated. It is less gruesome than what we have now in the NTP code, but it is still a gruesome hack. There are far to many problems in this that you don't consider: 1) Computers booting inside your 1000 second interval do what ? 2) What about a computer being offline (by design or accidentally) during the 1000second window ? 3) Many real time systems will not tolerate 1e-3 clock error. 4) How wold a leap-time aware application run on such an operating system ? 5) You still need to way to distribute leapseconds to embedded and offline computers. Your proposal pastes over some of the minor issues with leap seconds, but it doesn't address the two fundamental problems: 1. You don't know when they will happen with long enough warning. 2. You can't test one when you need to. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.
Re: two world clocks AND Time after Time
In message [EMAIL PROTECTED], Steve Allen writes: On Mon 2005-01-24T00:50:10 -0800, Tom Van Baak hath writ: Isn't knowing when noon is already a specialist operation? I mean, most people could tell you when noon is to within an hour or two or three, but finer than that requires a far amount of daily mental calculation, no? Noon has long required a calendar, an almanac, a longitude, and the ability to perform addition and subtraction. You forget a lawyer or at least a copy of the relevant laws in your area, because surely you're not assuming that my watch runs on UTC ? -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.
Re: two world clocks AND Time after Time
Steve Allen scripsit: What we are being told by the Time Lords is that, starting from a date in the near future, knowing when noon is will also be a specialist operation. Already true. For many months of the year, solar noon is closer to 1 PM, or even 1:30 PM, in a great many countries, and how many people actually realize *that*? -- Winter: MIT, John Cowan Keio, INRIA,[EMAIL PROTECTED] Issue lots of Drafts. http://www.ccil.org/~cowan So much more to understand! http://www.reutershealth.com Might simplicity return?(A tanka, or extended haiku)
Re: Time after Time
Poul-Henning Kamp wrote on 2005-01-23 09:00 UTC: any leap hours that prevented this would, if ever implemented, be even more traumatic than leap seconds are now. they already happen here twice a year, and by now even Microsoft has gotten it right. OBJECTION, your Time Lords! UTC currently certainly has *no* two 1-h leaps every year. What the witness tries here is merely a poor attept to confuse the jury. He muddles the distinction between local civilian time, which we all know is entirely subject to our politicians deep-seated desires to manipulate us into getting out of bed earlier in summer, and UTC, which is what all modern computers use internally for time keeping today, below the user interface, where a 1-h leap is entirely unprecedented and uncalled for. [By the way, and for the record, may I remind the jury that the quoted Microsoft *is* actually the one large operating-system vendor who still has not quite yet gotten it right, as all Windows variants still insist on approximating in the PC BIOS clock LCT instead of UTC. Rebooting during the repeat hour after DST *will* corrupt your PC's clock. Gory details: http:// www.cl.cam.ac.uk/~mgk25/mswish/ut-rtc.html ] In addition to being historically unprecedented, such a move would be illegal in the United States and some other countries, which have laws explicitly defining their time zones based on solar mean time, unless such laws were changed. The laws, wisely, do not say how close to solar mean time, and parts of USA already have offsets close to or exceeding one hour anyway. As Ron Beard said wisely in his opening address in Torino, laws can be changed fairly easily, and this discussion should certainly not be about reinterpreting *past* legislation. Instead, it should be entirely about making a scientific, technical, and practical recommendation for *future* legislation. If you read, just one example, to deviate a bit from the overwhelmingly US/UK-centricism of this legal argument, the relevant German legislation, http://www.cl.cam.ac.uk/~mgk25/time/zeitgesetz.en.html then you will find that it consists at the moment simply of a pretty exact technical description of UTC. In other words, it follows exactly the relevant ITU recommendation! If the ITU recommendation were changed, for a good cause and with wide international consensus, I have little doubt that the German parliament and pretty much every other parliament would be sympathetic and update the national legislation accordingly. German laws are already updated almost each time the BIPM revises some aspect of the SI. Countries update their national radio interference and spectrum management legislation regularly based on the international consensus that is being negotiated within the ITU. The US and UK are actually no different from that, except that the subtle differences between GMT and UTC have escaped political attention in these two countries so far, and as a result, they still have a technically rather vague definition of time in their law books, and leave in practice all the details up to the Time Geeks as USNO, NPL, etc. If you think that discussions within the ITU should feel constrained by the legislation of individual member countries, as opposed to setting guidelines for future legislation there, then you have simply misunderstood the entire purpose of the process. Markus -- Markus Kuhn, Computer Lab, Univ of Cambridge, GB http://www.cl.cam.ac.uk/~mgk25/ | __oo_O..O_oo__
Re: Time after Time
Markus Kuhn scripsit: UTC currently certainly has *no* two 1-h leaps every year. There seems to be persistent confusion on what is meant by the term leap hour. I understand it as a secular change to the various LCT offsets, made either all at once (on 1 Jan 2600, say) or on an ad-lib basis. You seem to be using it in the sense of a 1h secular change to universal time (lower-case generic reference is intentional). Can anyone quote chapter and verse from Torino to show exactly what was meant? Or is the text in fact ambiguous? If you read, just one example, to deviate a bit from the overwhelmingly US/UK-centricism of this legal argument, I keep talking about the Chinese example. Consider the city of Kashi, population about 175,000. Its longitude is about 76 E, which means that its LMT is about GMT+5. Its LCT, however, is Asia/Shanghai, or UTC+8. If all those people can live with an LCT that is three hours away from the sun, we can stand rather lower discrepancies just fine. -- Don't be so humble. You're not that great. John Cowan --Golda Meir[EMAIL PROTECTED]
Re: two world clocks AND Time after Time
On Thu 2005-01-20T14:59:18 -0700, Rob Seaman hath writ: Leap seconds are a perfectly workable mechanism. Systems that don't need time-of-day should use TAI. Systems that do need time-of-day often benefit from the 0.9s approximation to UT1 that UTC currently provides. Let's stop pretending that *both* atomic time and time-of-day are not needed. Instead, let's direct our efforts toward implementing improved systems for conveying both of these fundamental timescales to users of both precision and civil time. On Sat 2005-01-22T20:43:51 -0500, Daniel R. Tobias hath writ: Now, if a time standard is to be defined based solely on constant SI seconds, with no reference to astronomy, then why even include all the irregularities of the Gregorian Calendar, with its leap year schedule designed to keep in sync with the Earth's revolutions? It really makes no sense that TAI includes days, years, and so on at all, and this will seem particularly senseless when the current date by TAI is a day or more removed from Earth-rotational time, as will happen in a few millennia. What is really needed is two different time standards: a fixed- interval standard consisting solely of a count of SI seconds since an epoch (no need for minutes, hours, days, months, and years), and a civil-time standard that attempts, as best as is practical, to track the (slightly uneven) motions of the Earth. Of course there are other units of time in civil history which have been converted from actual representations into conventional ones. Sailors have no qualms about calling out the next high tide in terms of local civil time (now practically based on UTC). They all know that the times shift by around an hour every day. The month lost its connection with the moon early in the Roman era. Everybody knows, and in general nobody cares, that the moon is not new at the beginning of a month in the Gregorian calendar. The Gregorian year is pretty good, but three millenia hence the vernal equinox will have drifted discernably from the original intent. In general nobody cares about the date of Easter that much, and (as seen in Duncan Steel's book) even some of the best astronomers have not understood the distinction between the tropical year (as popularly defined by Newcomb) and the Vernal Equinox Year that Pope Gregory's calendar actually aimed to match. Above Rob Seaman and Danial Tobias have echoed some of the issues discussed by Essen himself in his autobiographical work Time for Reflection which his son-in-law has reproduced at http://www.btinternet.com/~time.lord/ In particular, this footnote http://www.btinternet.com/~time.lord/TheAtomicClock.htm#_msocom_1 (and the entire chapter containing it) reveals that the tension between the physicists and the astronomers (notably Stoyko, who has largely been written out of history) was great enough that there almost became two SI units for time, one being the second based on the day, and one being the Essen based on the cesium resonance. But Essen claims for himself (in both this autobiography and in Metrologia http://www.bipm.org/metrologia/ViewArticle.jsp?VOLUME=4PAGE=161-165 ) the credit for recognizing that the existing systems of time distribution (and now presumably extended to time computation) basically cannot be expected to tolerate the existence of two kinds of time. I don't think this is really true anymore, but it is admittedly costly. It was the astronomers who first made the mistake of counting a truly uniform time scale using the calendrical/sexagesimal notation originally based on earth rotations (and now concisely communicated using ISO 8601). It was the physicists who pushed to continue the practice. Knowing the tides is a specialist operation, and has always been. Knowing the phase of the moon is a specialist operation, and has been in western culture for over two millenia. What we are being told by the Time Lords is that, starting from a date in the near future, knowing when noon is will also be a specialist operation. Month is entirely conventional in its meaning. Year is entirely conventional in its meaning. So soon day will be entirely conventional in its meaning. All of them become predictable, albeit upon examination silly, extensions of things which originally meant something else. The priesthood of astronomy has become irrelevant to the general populace, and the priesthood of the physicists has taken precedence. The trick will be to educate the general public that 12:00 means slightly less about where the sun is in longitude than the Gregorian calendar date means about where the sun is in latitude. Both of these schemes fail, it's just that atomic time fails by a full hour within 1000 or so years whereas the Gregorian calendar fails by a full day only after another 2000 or so years. I really like sundials, mean solar time, and the analemma. I think it is disingenuous to use the methods we see being used by the atomic clock keepers to
Time after Time
I sure hope that the future of mankind's timekeeping systems doesn't get decided by an Internet flame war between contending groups of geeks... As I see it, the dispute comes from the fact that people want two different, irreconcilable types of time, time of day (earth/solar angle) and constant interval time. Traditionally (over all of human history), civil time has always related in some way to solar-angle time, originally directly, and now in a complex, artificial way with confusing politically-imposed irregularities such as daylight saving time and wildly gerrymandered time zones. It still does relate to solar time, however, with the local clock time at a given point on Earth at a particular time of year generally fixed at a constant increment from solar mean time for that spot (but sometimes changing to a different increment for part of the year). There's no prospect that eventually, due to discrepancies in the system, noon will come when it's dark (except perhaps very near the north or south poles). Some of the proposals, however, seek to decouple civil time altogether from solar time, an unprecedented step which would possibly lead to day and night being completely reversed; any leap hours that prevented this would, if ever implemented, be even more traumatic than leap seconds are now. In addition to being historically unprecedented, such a move would be illegal in the United States and some other countries, which have laws explicitly defining their time zones based on solar mean time, unless such laws were changed. Now, if a time standard is to be defined based solely on constant SI seconds, with no reference to astronomy, then why even include all the irregularities of the Gregorian Calendar, with its leap year schedule designed to keep in sync with the Earth's revolutions? It really makes no sense that TAI includes days, years, and so on at all, and this will seem particularly senseless when the current date by TAI is a day or more removed from Earth-rotational time, as will happen in a few millennia. What is really needed is two different time standards: a fixed- interval standard consisting solely of a count of SI seconds since an epoch (no need for minutes, hours, days, months, and years), and a civil-time standard that attempts, as best as is practical, to track the (slightly uneven) motions of the Earth. When other planets are settled, they'll need their own local time standards too (NASA is already doing this for Mars). -- == 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/
