Re: Consensus rather than compromise
On Mon 2005/09/05 09:15:18 +0100, "Clive D.W. Feather" wrote in a message to: LEAPSECS@ROM.USNO.NAVY.MIL >I actually doubt that bit. For example, the whole USA would move in one go, >and so would the whole EU (which now stretches over 4 - I think - hourly >bands). With those examples in mind, I suspect most other countries would >co-ordinate to some extent. The great thing about the Egyptian empire is that it lasted so long - Cleopatra is closer to us in time than she was to the pyramid builders. However, I wouldn't bet on either the US or the EU existing in one thousand years. Mark Calabretta ATNF
Re: Consensus rather than compromise
On Fri 2005/09/02 10:10:23 -0400, "John.Cowan" wrote in a message to: Mark Calabretta <[EMAIL PROTECTED]> and copied to: Leap Seconds Issues >Well, central Australia only transitioned from UTC+9h to UTC+9h30m a >few decades ago. Is the reason for doing this still known? I seem to remember CST always being 30m behind AEST; from the zoneinfo file the transition seems to have occurred in 1899. The 1971 date for South Australia appears to be for a change in DST rules. >A great image! Among island groups I noticed a tendency for boundary excursions mostly to go westwards - essentially amounting to permanent daylight savings. However, that map definitely needs a better colour-coding scheme. >Certainly the first is true, but I'm far from sure about the second point. >(Note that the term "leap hour" probably shouldn't be used for this >scheme, as it invites confusion with the plan to insert an hour into >universal time. We need a punchy name for it.) :z I'd like to be around when they try to add an hour to UTC! But I guess the whole point of the ITU proposal is that noone alive today will be. Mark Calabretta ATNF
Re: Consensus rather than compromise
Mark Calabretta scripsit:
> Also, as Rob Seaman points out, the very fact that these half-hour
> zones exist suggests that a half-an-hour difference in solar time
> matters very much to some.
Well, central Australia only transitioned from UTC+9h to UTC+9h30m a
few decades ago. Is the reason for doing this still known?
>awk '{print $1, $2}' zone-changes.txt | sort -u
I did that too. :-)
> [B]ut it would be useful to have dates associated with these entries -
> many would come from the first few decades of the 1900s when the time
> zones were settling into place.
I'll try to whack on the code to generate a four-column version of the
table.
> However, it still doesn't affect the first part of my argument. To
> understand why, imagine the typical timezone map such as that at
> http://en.wikipedia.org/wiki/Time_zone, or at the front of any decent
:z
> atlas, but colour-coded so that red at +12 grades through the rainbow
> to violet at -12.
A great image!
> (BTW, that also applies to Kiribati with the date line.)
BTW, just in case anyone thought otherwise, that wasn't a Y2K publicity
stunt (at least not in origin). It's a big nuisance having a country
where the date depends on your location: recordkeeping becomes very difficult
and unreliable, and people crossing from island to island, especially those
who did so daily or weekly, had a very hard time.
> Now imagine how the map would change if leap hours were introduced; you
> should notice two things, firstly a secular change such that each place
> on the map becomes progressively redder, and secondly a progressive
> fragmentation of the boundaries as each administration decides
> independently what to do with the leap hour.
Certainly the first is true, but I'm far from sure about the second point.
(Note that the term "leap hour" probably shouldn't be used for this
scheme, as it invites confusion with the plan to insert an hour into
universal time. We need a punchy name for it.) :z
Another thing that would happen, very likely, is the use of large negative
offsets. I think that people would be quite unwilling to move their
countries across the Date Line even if it could be done all at once.
By great good fortune, the 180 degree meridian crosses land in very
few places, and the Date Line is bent around those so that there is no
place where it corresponds with a land boundary. Having the date change
when crossing a land frontier would be almost as bad as having it divide
a country.
--
John Cowan [EMAIL PROTECTED] www.reutershealth.com www.ccil.org/~cowan
The present impossibility of giving a scientific explanation is no proof
that there is no scientific explanation. The unexplained is not to be
identified with the unexplainable, and the strange and extraordinary
nature of a fact is not a justification for attributing it to powers
above nature. --The Catholic Encyclopedia, s.v. "telepathy" (1913)
Re: Consensus rather than compromise
On Thu 2005/09/01 10:46:57 -0400, "John.Cowan" wrote
in a message to: LEAPSECS@ROM.USNO.NAVY.MIL
>(N.B. The 1896 shift is *not* the reason Broken Hill is separated
>from Sydney, since that event took place before the Epoch. Rather,
>it is because Broken Hill adopted Adelaide's DST rules in 2001.)
zoneinfo's fragmentation, the Broken Hill (Yankowinna) effect if you
like, already illustrates the second part of my argument. Also, as
Rob Seaman points out, the very fact that these half-hour zones exist
suggests that a half-an-hour difference in solar time matters very much
to some.
>I have done some work on the zoneinfo source data to generate a three-
>column table summarizing the changes in the world's 365 time zones.
>The table can be downloaded from http://www.ccil.org/~cowan/zone-changes.txt .
Thanks for the list, I freely admit that there are many more recent
changes than I had expected, though I think the fragmentation effect
tends to magnify the number. For my purposes filtering the list as
follows
awk '{print $1, $2}' zone-changes.txt | sort -u
produces something closer to what I had in mind, but it would be useful
to have dates associated with these entries - many would come from the
first few decades of the 1900s when the time zones were settling into
place.
However, it still doesn't affect the first part of my argument. To
understand why, imagine the typical timezone map such as that at
http://en.wikipedia.org/wiki/Time_zone, or at the front of any decent
atlas, but colour-coded so that red at +12 grades through the rainbow
to violet at -12. Now imagine a movie of how that map has changed over
time as described by zoneinfo. In your mind's eye you should see that
the map basically stays the same but with a degree of jitter in the
boundaries either to the east or west by up to an hour or so, which
essentially amounts to permanent daylight savings being enabled or
disabled. (BTW, that also applies to Kiribati with the date line.)
Mistaking the time zone should not produce errors of more than an hour
(mostly).
Now imagine how the map would change if leap hours were introduced; you
should notice two things, firstly a secular change such that each place
on the map becomes progressively redder, and secondly a progressive
fragmentation of the boundaries as each administration decides
independently what to do with the leap hour.
Mark Calabretta
ATNF
Re: Consensus rather than compromise
On Sep 1, 2005, at 7:46 AM, John.Cowan wrote: The table can be downloaded from http://www.ccil.org/~cowan/zone- changes.txt . Data - cool! Thanks. The first column is the zone name in the form "continent/ city" (city names are more stable than country or state/province names). Yeah, that's what Apple does, for instance, in their timezone preferences. Note that this really wants to be a list of political/ geographic entities with the authority to make their own choices, not simply a list of ones who have done so in the past. That the Hopi Nation is in the same timezone as Arizona may or may not be up to them. Whether they observe DST and with what rules is a matter of their sovereignty. Just as a matter of interest, I also discovered that as of right now there are 37 different time offsets in use: the integral hour offsets from -11h to +14h, plus the following: -9h30m (Pacific/Marquesas), -3h30m (America/St_Johns), +3h30m (Asia/Tehran), +4h30m (Asia/Kabul), +5h30m (Asia/Calcutta), +5h45m (Asia/Katmandu), +6h30m (Asia/Rangoon), +9h30m (the Yellow-Dog Dingo zones), +10h30m (Australia/Lord_Howe), +11h30m (Pacific/Norfolk), and +12h45m (Pacific/Chatham). Isn't this clear evidence that societies worldwide recognize the primacy of solar time? What possible explanation other than synchronization with the sun (or stars) could be offered for a quarter or half hour offset? Clearly these localities would regard noon=light and midnight=dark as too course a constraint. Whatever solutions are entertained to the challenge of civil time, an appropriate recognition of solar time should be included in the requirements. Of course there are means of coordinating them. The EU is one such means, and the federal U.S. and Australian governments are another. But in the end LCT is an attribute of sovereignty, and individual governments will give up just as much control as suits them. Indeed, but one might expect that these governments would prefer to be given some hints from the experts as to appropriate policies. The notion of a leap hour may or may not correspond to appropriate policy. Wouldn't it be easier to make the case in support of this policy change if there were some detailed plan developed for what effect leap hours and large values of DUT1 might have in the future? Might not officials from the Marquesas through Chatham, let alone Tehran and Calcutta, wish to be consulted and advised? Rob Seaman National Optical Astronomy Observatory
Re: Consensus rather than compromise
Mark Calabretta scripsit: > But DST is not the same as TZ - all these states are still basically > UTC+10 and are not likely to change (that would probably be a federal > issue anyway), so rationality is restored in winter! The world's > timezones are pretty stable now after a few minor adjustments earlier > last century. Well, you can call it "minor" if you want, but when two-thirds of the world's zones have changed at least once, that makes it look to me like the rule, not the exception. Australia *has* been pretty stable: its eleven zones (Adelaide, Brisbane, Broken Hill, Currie, Darwin, Hobart, Lindeman, Lord Howe, Melbourne, and Perth) have all remained fixed in offset since the beginning of LCT in 1895, except for the 1896 shift of Broken Hill from UTC+10h to UTC+9h, the 1971 shift of Adelaide, Broken Hill, and Darwin from UTC+9h to UTC+9h30m, and the 1981 shift of Lord Howe from UTC+10h to UTC+10h30m. (N.B. The 1896 shift is *not* the reason Broken Hill is separated from Sydney, since that event took place before the Epoch. Rather, it is because Broken Hill adopted Adelaide's DST rules in 2001.) I have done some work on the zoneinfo source data to generate a three- column table summarizing the changes in the world's 365 time zones. The table can be downloaded from http://www.ccil.org/~cowan/zone-changes.txt . The first column is the zone name in the form "continent/city" (city names are more stable than country or state/province names). The second column is the LCT offset. The third column is a name showing which of the 124 different sets of DST rules was in effect, or numeric value showing that DST was (during some period) always in effect, or a hyphen if DST was not in effect. The order of the rows does *not* reflect the historical order of changes. The columns are tab-separated. I have also posted the raw data, filled with helpful comments, at http://www.ccil.org/~cowan/timezones.txt . I have not included the Antarctica information. > Quirky exceptions like Kiribati, as noted by John Cowan, > are so uncommon that they generate interest and don't really affect the > argument. Kiribati is exceptional because of the magnitude of the change. But massaging the above data shows that Asia/Singapore, Asia/Kuala_Lumpur, and Asia/Jakarta have changed their offsets six times each, and that Europe/Vilnius, Europe/Simferopol, Europe/Chisinau, and Asia/Pontianak have changed theirs five times each, some quite recently. Just as a matter of interest, I also discovered that as of right now there are 37 different time offsets in use: the integral hour offsets from -11h to +14h, plus the following: -9h30m (Pacific/Marquesas), -3h30m (America/St_Johns), +3h30m (Asia/Tehran), +4h30m (Asia/Kabul), +5h30m (Asia/Calcutta), +5h45m (Asia/Katmandu), +6h30m (Asia/Rangoon), +9h30m (the Yellow-Dog Dingo zones), +10h30m (Australia/Lord_Howe), +11h30m (Pacific/Norfolk), and +12h45m (Pacific/Chatham). > The proposal to introduce leap hours, with no means of coordinating > them, means that the time zones themselves, will change secularly but > in a disorganized manner. Of course there are means of coordinating them. The EU is one such means, and the federal U.S. and Australian governments are another. But in the end LCT is an attribute of sovereignty, and individual governments will give up just as much control as suits them. -- John Cowan www.ccil.org/~cowan www.reutershealth.com [EMAIL PROTECTED] Economists were put on this planet to make astrologers look good. --Leo McGarry
Re: Consensus rather than compromise
In message: <[EMAIL PROTECTED]> Ed Davies <[EMAIL PROTECTED]> writes: : All I was trying to say is that if a system is sufficiently isolated : that it can't easily be updated with leapsecond information then it : probably doesn't matter too much if times _within_ that system are : offset from UTC by a second or so. The problem is that once you start running your system time in TAI and then reporting UTC based on leap second tables, those tables necessarily must be up to date, or this operation will fail. It has nothing to do with having the leap second happen at the right time while time is playing forward. The problem comes when one takes time stamps and tries to do useful things with them later, or exchange them with other parties. I'll be the first to admit that my system in the middle of nowhere is an extreme case. It is designed to show the limiting effects of randomly scheduled leap seconds. Time keeping devices that are accurate to 200us over the period of time we schedule leap seconds are relatively cheap these days and having randomly scheduled leap seconds artificially limits how long one can flywheel UTC when disconnected from sources of leap seconds. Warner
Re: Consensus rather than compromise
On Thu 2005/09/01 07:37:04 +0200, "Poul-Henning Kamp" wrote in a message to: Mark Calabretta <[EMAIL PROTECTED]> and copied to: Leap Seconds Issues >What makes you think politicians will stop messing with timezones >in the future ? > >Remember how several Pacific island nations jumped the date-line, >(some for very handsome payments) in order to be the first to >experience the Y2K problem ? I'm distinguishing between time zones and daylight-savings rules. It's true that DST is a political football, around here it's country versus city - the farmers don't want to milk their cows before sunrise, etc. On the east coast of Australia now for a few weeks each year Tasmania (which being southerly goes early), NSW, Victoria, and Queensland (which decided by referendum in 1994 that it didn't want daylight savings anymore!) are all on different daylight saving time. This makes life interesting for those living in towns that straddle state borders. But they're all in the same longitude zone and once used to be synchronized. But DST is not the same as TZ - all these states are still basically UTC+10 and are not likely to change (that would probably be a federal issue anyway), so rationality is restored in winter! The world's timezones are pretty stable now after a few minor adjustments earlier last century. Quirky exceptions like Kiribati, as noted by John Cowan, are so uncommon that they generate interest and don't really affect the argument. But note that Kiribati actually changed its date, not its time, by skipping a calendar day. The proposal to introduce leap hours, with no means of coordinating them, means that the time zones themselves, will change secularly but in a disorganized manner. Mark Calabretta ATNF
Re: Consensus rather than compromise
Ed Davies wrote: : (running to their own little timezone not being good enough), M. Warner Losh wrote: Might I suggest that digs like this make rational discussions difficult? I'm sorry you read that as a dig. That was not what I was intending. All I was trying to say is that if a system is sufficiently isolated that it can't easily be updated with leapsecond information then it probably doesn't matter too much if times _within_ that system are offset from UTC by a second or so. In effect, the uncorrected time used within the system becomes a sort of local timezone - in the same way that GPS time which is UTC from some date but ignoring more recent leap seconds could be thought of as a timezone. Ed Davies.
Re: Consensus rather than compromise
In message <[EMAIL PROTECTED]>, Steve Allen writes: >I ponder whether the current effort to redefine UTC might create a >fragmentation of practice which would violate "offsets from a common >reference time" and make the situation much uglier. It is not clear >whether the pressures of economics and trade can override tradition >and national pride. Not to mention the religious wars and the following crusades to "bring proper solar time to the infidels" etc etc. Yes, interesting times ahead indeed. -- 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: Consensus rather than compromise
On Wed 2005-08-31T22:57:42 -0400, John.Cowan hath writ: > Fortunately, it's not that bad. All 365 current zones define > their LCTs using a list of offsets from a common reference time. The current effort to abolish leap seconds completely violates the subject line of this thread. There is no consensus or compromise, there is only fiat. We see at least the UK government unwilling to support the change, and the official at the IERS who is accorded the responsibility to call for leaps unwilling to support the change. I ponder whether the current effort to redefine UTC might create a fragmentation of practice which would violate "offsets from a common reference time" and make the situation much uglier. It is not clear whether the pressures of economics and trade can override tradition and national pride. -- Steve Allen <[EMAIL PROTECTED]>WGS-84 (GPS) UCO/Lick ObservatoryNatural Sciences II, Room 165Lat +36.99858 University of CaliforniaVoice: +1 831 459 3046 Lng -122.06014 Santa Cruz, CA 95064http://www.ucolick.org/~sla/ Hgt +250 m
Re: Consensus rather than compromise
In message <[EMAIL PROTECTED]>, Mark Calabretta writes: > >On Wed 2005/08/31 07:29:22 +0200, Poul-Henning Kamp wrote >in a message to: LEAPSECS@ROM.USNO.NAVY.MIL > >>>If such a system were to be adopted, then in future, in order to >>>determine a historical time, the full record of timezone changes would >>>be needed. >> >>How is this different than today ? > >To determine the civil time in Copenhagen at a specified epoch we take >UTC, add the timezone offset then possibly add 1 hour for DST. zoneinfo >provides rules for the latter - e.g. DST starts on the first week of >March and ends whenever. I think you misunderstood the question, so let me rephrase it: What makes you think politicians will stop messing with timezones in the future ? Remember how several Pacific island nations jumped the date-line, (some for very handsome payments) in order to be the first to experience the Y2K problem ? You've seen the "energy savings" US Congress just enacted. No matter what we do in the scientific world, timezones will remain a political subject. -- 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: Consensus rather than compromise
Rob Seaman scripsit: > 2) It is different because today timezones and related issues like > Daylight Saving are purely periodic phenomena. For most purposes - > including interval purposes - you only need to know the zone and DST > status at the beginning and end of whatever period of interest. That turns out not to be the case. > 3) It is different because today there is a single list of historical > leap seconds, and a TZ based system, as Cowan points out, would be at > the whims of local jurisdictions worldwide. It already is. > One imagines a new discipline similar to the tree ring counting of > dendrochronology whose goal would be to synchronize timestamped data > from different localities and epochs. These chronochronologists would > be responsible for building overlapping longitudinal historical clock > records from hundreds of distinct locations worldwide. Fortunately, it's not that bad. All 365 current zones define their LCTs using a list of offsets from a common reference time. For each such offset, we must keep track of whether it is a standard or daylight-savings offset and during what range of moments it was in effect. That's essentially what the files under /usr/share/zoneinfo contain, in binary form. Consequently, given a particular moment in one time zone given as year-month-day-hour-minute-second plus an indication of whether the moment is in DST or not (to compensate for the fact that some LCT clock readings labels refer to two separate moments), you can generate equivalent information for every other zone without problem. > 4) It is different precisely because for short periods the existence > of leap seconds can often be ignored for purposes that require > accuracy at the level of a minute or so. Presumably a TZ/DST based > system would operate in larger discontinuities, e.g., leap hours, > that might be very difficult to ignore indeed. Agreed, which is why people particularly concerned with a given zone would be at pains to update their information in a timely fashion. Systems that don't care what LCT zone they are in wouldn't have to worry about it. -- John Cowan [EMAIL PROTECTED] www.reutershealth.com www.ccil.org/~cowan This great college [Trinity], of this ancient university [Cambridge], has seen some strange sights. It has seen Wordsworth drunk and Porson sober. And here am I, a better poet than Porson, and a better scholar than Wordsworth, somewhere betwixt and between. --A.E. Housman
Re: Consensus rather than compromise
Mark Calabretta scripsit: > Currently the timezone offset is essentially fixed for a particular > place, yes there are quirks but it's hardly relevant to the argument. If by "currently" you mean "at this very moment", then that's trivially true. If by "currently" you mean "in the last few decades", then it's false. Zoneinfo currently recognizes 365 distinct localities on the basis of nationality or distinct history (since the Epoch, some 1125539538 seconds ago) or both. Of these, only 129 have had a fixed offset since the beginning of LCT in that locality. And of those, 55 have changed their DST rules at least once, leaving only 74 that have been entirely stable. > Under the proposed scheme, timezone offsets would be a function of epoch > as well as place, thus requiring another table for each timezone. This is already the case: nothing new is needed. > However, there would be a fundamental difference between the DST and TZ > rules: the former are quantized at 0 or +1, so you can only ever get it > wrong by one hour. However, the TZ offset would not be limited in > range, over millenia it would span many hours, one hour in the first > millenium and accelerating. Eastern Kiribati has already changed from UTC-10 to UTC+14, a 24-hour discrepancy. It'll be a long time before any rotationally induced offset changes will amount to that. Eventually, of course, it'll be impossible to maintain the fiction that the Earth rotates in anything like 24 hours. IIRC the maximum possible slowing before the Earth becomes tidally locked to the Moon is 47 current days; when an "hour" lasts almost two sleep-wake cycles, the current clock will *have* to be revised. > John Cowan argues that timezones will tend to coalesce as nations reach > agreement, but remember that we are talking about timescales of > millenia. Over such times nations as a whole don't tend to reach > agreement - consider how the Gregorian calendar was adopted piecemeal by > different countries (empires really) over centuries. A process which is now essentially complete, however. A few countries still use other calendars officially, but the Gregorian calendar is well-known there anyhow. No novel calendar has been adopted anywhere since 1583. > But the killer is that a timezone only needs to fragment *once* in order > to require the creation of a separate TZ rule table. Quite so, but what of it? People who do not care about LCT in the new locations can ignore the table update; those who do care have a strong incentive to download the new tables. Systems that need not worry about LCT, need not care at all. -- While staying with the Asonu, I met a man from John Cowan the Candensian plane, which is very much like [EMAIL PROTECTED] ours, only more of it consists of Toronto. http://:www.ccil.org/~cowan --Ursula K. Le Guin, Changing Planes
Re: Consensus rather than compromise
On Wed 2005/08/31 07:29:22 +0200, Poul-Henning Kamp wrote in a message to: LEAPSECS@ROM.USNO.NAVY.MIL >>If such a system were to be adopted, then in future, in order to >>determine a historical time, the full record of timezone changes would >>be needed. > >How is this different than today ? To determine the civil time in Copenhagen at a specified epoch we take UTC, add the timezone offset then possibly add 1 hour for DST. zoneinfo provides rules for the latter - e.g. DST starts on the first week of March and ends whenever. Currently the timezone offset is essentially fixed for a particular place, yes there are quirks but it's hardly relevant to the argument. Under the proposed scheme, timezone offsets would be a function of epoch as well as place, thus requiring another table for each timezone. However, there would be a fundamental difference between the DST and TZ rules: the former are quantized at 0 or +1, so you can only ever get it wrong by one hour. However, the TZ offset would not be limited in range, over millenia it would span many hours, one hour in the first millenium and accelerating. John Cowan argues that timezones will tend to coalesce as nations reach agreement, but remember that we are talking about timescales of millenia. Over such times nations as a whole don't tend to reach agreement - consider how the Gregorian calendar was adopted piecemeal by different countries (empires really) over centuries. Consider the way the map of Europe has changed since the Roman Empire, or even over the last couple of centuries, or even within our own lifetimes. And consider also the disparate and antagonistic nature of political ideologies in those periods. But the killer is that a timezone only needs to fragment *once* in order to require the creation of a separate TZ rule table. >How is it different from having to keep a total history of leapseconds ? The table of leapseconds is a function of time but not place. Mark Calabretta ATNF
Re: Consensus rather than compromise
Poul-Henning Kamp replying to Mark Calabretta: If such a system were to be adopted, then in future, in order to determine a historical time, the full record of timezone changes would be needed. How is this different than today ? How is it different from having to keep a total history of leapseconds ? 1) It is different because today civil time is based on solar time and the issue can be ignored completely for situations in which the solar time on a given historical date was of principal importance. Solar time is equivalent to (a simple function of) Earth orientation, which is a reflection of a physical phenomenon. TAI is merely a reflection of interval time. We may disagree on whether solar time is of sufficient importance to drive public policy, but TAI in and of itself certainly is not. 2) It is different because today timezones and related issues like Daylight Saving are purely periodic phenomena. For most purposes - including interval purposes - you only need to know the zone and DST status at the beginning and end of whatever period of interest. If the TZ system is used, on the other hand, to correct for a residual drift in a mismatch between civil and solar time, Calabretta's statement becomes a very strong factor. 3) It is different because today there is a single list of historical leap seconds, and a TZ based system, as Cowan points out, would be at the whims of local jurisdictions worldwide. One imagines a new discipline similar to the tree ring counting of dendrochronology whose goal would be to synchronize timestamped data from different localities and epochs. These chronochronologists would be responsible for building overlapping longitudinal historical clock records from hundreds of distinct locations worldwide. 4) It is different precisely because for short periods the existence of leap seconds can often be ignored for purposes that require accuracy at the level of a minute or so. Presumably a TZ/DST based system would operate in larger discontinuities, e.g., leap hours, that might be very difficult to ignore indeed. 5) It is different because currently a longitudinal correction for multiple leap seconds is required to recover TAI from UTC at some historical epoch. This suggestion would require such a longitudinal correction to recover actual UT from civil time. The current reality is that users of TAI already have transport options such as GPS that are at least a good as UTC. The TZ/DST system would provide no backup mechanism for transporting universal time. The importance of all these and similar issues is a matter of debate. The debate should be backed up with data that can be used to derive requirements and use cases for whatever future civil time standard comes next. Rob Seaman National Optical Astronomy Observatory
Re: Consensus rather than compromise
Rob Seaman scripsit: > It does sound like we are being encouraged to replace the worldwide > timezone system *What* worldwide timezone system? The nations of the world have agreed (more or less) on a common international reference time, GMT/UTC. But each of the 220+ sovereign nations defines its own LCT(s) for its own territory, as well as its own DST rules. For example, in the United States, it is the U.S. Department of Transportation (a federal agency) that decides which time zone a particular locality is in, but it is state law (or in one case, tribal law) that determines whether DST is observed there or not. Not even the so-called "International Date Line" is actually the product of international agreement: it's simply a line drawn to separate the countries in GMT+x zones from the countries in GMT-x zones. In 1995, the Date Line actually did move as Kiribati changed two of its three timezones from UTC-11 and UTC-10 to UTC+13 and UTC+14. Additionally, several parts of the world, notably Newfoundland in Canada, the whole of India, and the central part of Australia, have half-hour offsets from universal time. Liberia, indeed, was on UTC-0h44m30s until 1972; they are now on UTC+0. The only place there is a genuinely worldwide timezone system is on the high seas, where there is no national jurisdiction. Antarctica, which is also outside national jurisdiction, ignores longitude altogether: each base is on the timezone of the end of its supply line. > In an extreme analysis, the "fix it all in the timezones and leap > hours" proposal amounts to a return to nineteenth century practices > of clock time diverging between one railroad station and the next. > I don't believe that extreme would occur any more than you do, Then why bring it up? Nobody wants to return to what Isaac Asimov called "Podunk time for Podunk and Squeedunk time for Squeedunk". > And if a standard were to be implemented that relies on the tweaking > of local timezones to compensate for a drifting non-solar fundamental > reference, I think it inappropriate to refer to changes in offset of 30m or 1h as "tweaks". > it is not remarkable to expect that mechanisms for avoiding the slapdash > creation of ad hoc timezones and for allowing the appropriate tracking > of historical timestamps would be considered in advance and perhaps > be implemented under the force of law. Whose law? National laws create ad hoc timezones only if the nation desires them, and (as my previous posting mentioned) it generally doesn't. Most of the world's countries have only one timezone and are likely to stay that way, even if they wind up choosing a different, but still single, timezone eventually. > It isn't sufficient for any of us simply to claim that our own pet > proposal has no negative ramifications and to leave it at that. I don't. I simply think the negative ramifications are in scale with the ones we already have and know how to manage, and since they affect only LCT conversion, not elapsed time or time unit conversion, they are much less problematic. -- Possession is said to be nine points of the law,John Cowan but that's not saying how many points the law might have. [EMAIL PROTECTED] --Thomas A. Cowan (law professor and my father
Re: Consensus rather than compromise
On Aug 31, 2005, at 9:54 AM, M. Warner Losh wrote: : (running to their own little timezone not being good enough), Might I suggest that digs like this make rational discussions difficult? I agree with the general sentiment - after six years we're all a bit over sensitized and perhaps too willing to take shortcuts in both reading messages and writing our own replies. That said, irony does have a useful place in productive communication - even in highly technical discussions. I have to agree with Ed Davies' assessment of the mechanism being suggested. It does sound like we are being encouraged to replace the worldwide timezone system with the adoption of ad hoc local usage, perhaps down to the level of municipalities and isolated mountaintops. In an extreme analysis, the "fix it all in the timezones and leap hours" proposal amounts to a return to nineteenth century practices of clock time diverging between one railroad station and the next. I don't believe that extreme would occur any more than you do, but this is the area of phase space we're exploring at the moment. And if a standard were to be implemented that relies on the tweaking of local timezones to compensate for a drifting non-solar fundamental reference, it is not remarkable to expect that mechanisms for avoiding the slapdash creation of ad hoc timezones and for allowing the appropriate tracking of historical timestamps would be considered in advance and perhaps be implemented under the force of law. It isn't sufficient for any of us simply to claim that our own pet proposal has no negative ramifications and to leave it at that. Rob Seaman National Optical Astronomy Observatory
Re: Consensus rather than compromise
In message: <[EMAIL PROTECTED]> Ed Davies <[EMAIL PROTECTED]> writes: : M. Warner Losh wrote: : > Also, many systems just aren't connected to a public : > network, or aren't connected to a network at all, but still have a : > need to have knowledge of leap seconds. : > : : Can you give any examples of systems which need to follow : UTC to sub-second accuracy ... have a clock stable enough to : do so and yet are not connected by any mechanism which could : potentially provide leap-second information? First, your question is a bit of a red herring. More systems than just those are affected. If you have system time in TAI, and you want to convert to/from UTC, you must necessarily know all the leap seconds that have ever happend, or you can't do it. The classic example of a system that's not connected to any source of leap seconds is the spare sitting off in the corner. It has no knowledge of leap seconds that happened > 6 months after it was made, and has to acquire that knowledge somehow after it is first powered on. However, to answer your hypothetical question directly: Consider a system that has GPS steering a stable time source (say a cesium clock or rubidium standard). GPS goes away for some reason. You have a stable time source for a long period of time, yet no further knowledge of leap seconds. If the system is installed down the block, it is a simple matter to go out and fix the GPS antenna. If the system is in the middle of nowhere in alaska controlling timing signal automatically, it can take a while to get a crew out to fix it. Yet, it is highly desirable that it continue to work for as long as possible. Leap seconds artificially limit how long ntp will work on such a system, for example, because you can't flywheel more than about 6 months since after a leap second opportunity, you don't know if there was one or not. Of course, certain manual proceedures can be put into place for the above example. However, they are added complications that can't be dismissed out of hand. You have to design them well, or you get all kinds of weird edge case behavior. : (running to their own little timezone not being good enough), Might I suggest that digs like this make rational discussions difficult? Warner
Re: Consensus rather than compromise
M. Warner Losh wrote: Also, many systems just aren't connected to a public network, or aren't connected to a network at all, but still have a need to have knowledge of leap seconds. Can you give any examples of systems which need to follow UTC to sub-second accuracy (running to their own little time- zone not being good enough), have a clock stable enough to do so and yet are not connected by any mechanism which could potentially provide leap-second information? Presumably there are a few but I find them hard to imagine. Ed Davies
Re: Consensus rather than compromise
On Wed, Aug 31, 2005 at 11:14:17AM -0400, John.Cowan wrote: > Because there is far too much code that believes, for example, that if > you add 86400 to a time_t representing 2005-12-31T00:00UTC, you get a > time_t representing 2006-01-31T00:00UTC. Or that if you have a And then your whole office would be saying "I can't believe it's almost February! It seems like only yesterday it was December." -- trey valenta [EMAIL PROTECTED] seattle, wash. "The way to make a small fortune in the commodities market is to start with a large fortune."
Re: Consensus rather than compromise
Steve Allen scripsit: > Yet the zoneinfo needs to be updated numerous times per year at > unpredictable intervals as a result of arbitrary actions by > legislatures all over the world. Indeed, but the user has a substantial incentive to update to the latest data if directly affected by the change: the computer's clock will be wrong by an hour. The pressure to update to the latest leap-second table is far less. > The additional data required to handle leap seconds in the "right" > versions of zoneinfo is trivially smaller than the geopolitical data, > and the scheduling is more predictable. Granted. > If POSIX were to fix the definitions of time_t and epoch, why would > this not imply that handling leap seconds with Unix would become > trivial? Because there is far too much code that believes, for example, that if you add 86400 to a time_t representing 2005-12-31T00:00UTC, you get a time_t representing 2006-01-31T00:00UTC. Or that if you have a time difference in seconds, you can divide by 3600 and get one represented in hours. The upside of Posix is that time arithmetic is simple. The downside is that Posix sometimes lies about elapsed time and labels both a leap second and the preceding second with the same time_t. -- Newbies always ask: John Cowan "Elements or attributes? http://www.ccil.org/~cowan Which will serve me best?" http://www.reutershealth.com Those who know roar like lions; [EMAIL PROTECTED] Wise hackers smile like tigers. --a tanka, or extended haiku
Re: Consensus rather than compromise
In message: <[EMAIL PROTECTED]> Steve Allen <[EMAIL PROTECTED]> writes: : If POSIX were to fix the definitions of time_t and epoch, why would : this not imply that handling leap seconds with Unix would become : trivial? Because leap seconds are not trivial. If you make time_t a TAI-like thing, then you break all programs that do math to calculate a date and time since the usual "naive math" no longer works. You could fix these programs to use new APIs to do the math instead. However, you also enforce upon all systems a requirement to keep a leap second table up to date. While not so bad for systems that are constantly running, this can cause problems for people that maintain a stockpile of spare parts. These spares generally aren't on when leap updates occur and won't have them for some period of time after being deployed. Also, many systems just aren't connected to a public network, or aren't connected to a network at all, but still have a need to have knowledge of leap seconds. The class of functions that is defined as being continuous at all points, except where it isn't, while easy to understand can and is hard to implement correctly in all cases. Warner
Re: Consensus rather than compromise
On Wed 2005-08-31T09:16:33 -0400, John.Cowan hath writ: > That's exactly what /usr/share/zoneinfo is for, and even it buries all > historical timezone differences older than the Epoch, which was only 35 > years ago. We manage well enough: the total amount of data in binary > form is only 5 MiB, trivial by today's standards. Yet the zoneinfo needs to be updated numerous times per year at unpredictable intervals as a result of arbitrary actions by legislatures all over the world. The additional data required to handle leap seconds in the "right" versions of zoneinfo is trivially smaller than the geopolitical data, and the scheduling is more predictable. If POSIX were to fix the definitions of time_t and epoch, why would this not imply that handling leap seconds with Unix would become trivial? -- Steve Allen <[EMAIL PROTECTED]>WGS-84 (GPS) UCO/Lick ObservatoryNatural Sciences II, Room 165Lat +36.99858 University of CaliforniaVoice: +1 831 459 3046 Lng -122.06014 Santa Cruz, CA 95064http://www.ucolick.org/~sla/ Hgt +250 m
Re: Consensus rather than compromise
Mark Calabretta scripsit: > If such a system were to be adopted, then in future, in order to > determine a historical time, the full record of timezone changes would > be needed. For general purposes, a record would have to be maintained > for every civil administration that sets its timezone (I'm thinking of > /usr/share/zoneinfo). This would be a much bigger deal than the current > daylight saving switches. That's exactly what /usr/share/zoneinfo is for, and even it buries all historical timezone differences older than the Epoch, which was only 35 years ago. We manage well enough: the total amount of data in binary form is only 5 MiB, trivial by today's standards. > Inevitably it also means that the world's timezones would fragment > as adjacent civil administrations adopted disparate policies on timezone > adjustment. Why should they? It's annoying and expensive to be in a different zone from your neighbors and trading partners, which is why (e.g.) the bits of Indiana near Chicago and St. Louis are on Central Time and the bits near Cincinnati and Louisville are on Eastern Time instead of agreeing with the rest of the state. Not to mention why all of China is on UTC+8h despite LMT offsets varying from UTC+5h4m (Kashi again) to UTC+8h8m (Ningbo) and even a little beyond. I would expect just the reverse to happen: common agreements beyond national boundaries, as the EU countries have agreed to common DST transition events but not a common time zone. > And then, as the political map of the world changes, so > the record would become ever more hopelessly complicated. In fact /usr/share/zoneinfo has at least one zone for every country now, just in case Canada should decide on different DST transitions from the U.S. or something. (It has done so in the past, anyhow.) The offset adjustments required to keep TAI-based LCTs roughly in line with Earth rotation would be no different from what we already deal with routinely. -- By Elbereth and Luthien the Fair, you shall [EMAIL PROTECTED] have neither the Ring nor me! --Frodo http://www.ccil.org/~cowan
Re: Consensus rather than compromise
In message <[EMAIL PROTECTED]>, Mark Calabretta writes: >On Tue 2005/08/30 19:46:51 +0200, Poul-Henning Kamp wrote >in a message to: LEAPSECS@ROM.USNO.NAVY.MIL > >>keep "the clock" as people see it on their wrist [1] in sufficient >>sync with the light of day through minor acts of timezone adjustments. > >If such a system were to be adopted, then in future, in order to >determine a historical time, the full record of timezone changes would >be needed. How is this different than today ? How is it different from having to keep a total history of leapseconds ? -- 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: Consensus rather than compromise
On Tue 2005/08/30 19:46:51 +0200, Poul-Henning Kamp wrote in a message to: LEAPSECS@ROM.USNO.NAVY.MIL >keep "the clock" as people see it on their wrist [1] in sufficient >sync with the light of day through minor acts of timezone adjustments. If such a system were to be adopted, then in future, in order to determine a historical time, the full record of timezone changes would be needed. For general purposes, a record would have to be maintained for every civil administration that sets its timezone (I'm thinking of /usr/share/zoneinfo). This would be a much bigger deal than the current daylight saving switches. Inevitably it also means that the world's timezones would fragment as adjacent civil administrations adopted disparate policies on timezone adjustment. And then, as the political map of the world changes, so the record would become ever more hopelessly complicated. Mark Calabretta ATNF
Re: Consensus rather than compromise
On Aug 30, 2005, at 10:46 AM, Poul-Henning Kamp wrote: We could replace UTC with TAI, or kill leapseconds in UTC and let it keep its offset from TAI or do a myriad of other things and still keep "the clock" as people see it on their wrist [1] in sufficient sync with the light of day through minor acts of timezone adjustments. I challenge the use of the word "myriad" here, implying that there are 10,000 options. The broader we allow the civil time debate to range, the greater number of options, but many of those options are quite distinct from any situation similar to our current vision of an international civil time standard. I believe we will find at the end of the day, that is, the end of an appropriate international discussion of civil time for the third millennium, that civil time will continue to require that the concept of the solar day be reconciled with the concept of the second as an equal length unit of SI time. Note that I'm not trying to drive the discussion back to our well worn pathways - for the purposes of this message, I will entertain the notion of a leap hour as well as the notion of a leap second. But, simply combining the notion of the "day" as the unit of civil time (a "day" of whatever constant length), with the notion of a constant interval clock (atomic or otherwise) results in significant constraints to the search space for a solution. This would be true even on a planet without a moon that is stealing angular momentum. This would be true on a Earth with no historical Babylon to produce sexigesimal notation. The constraint as you word it is to allow corrections to correspond to "minor acts of timezone adjustments". This is 100% equivalent to saying that a civil day must mimic a solar day to a very narrow tolerance. If you want to get me to agree with you on something resembling the statement you made, then it is this: Local Legal/Civilian time will probably always have the sun highest in the sky somewhere around 12:00 through political modification of timezone affiliation. It follows trivially from there that it doesn't matter a dingos fetid kidneys [2] to legal/civilian time what UTC does with relation to the Sun, as long as it is not something ridiculous as monthly leapseconds. Again, I challenge the use of the word "trivially". And it does matter what UTC does with relation to the Sun - even for the extremes of the positions entertained in the original M&K article in GPS World. Please try to move my messages out of the category of "raving leap second supporter". I ain't talking about any of the issues that we have previously beaten to death. Civil Time for the 21st century will continue to mimic Mean Solar Time. What we have been debating all this time is the meaning of the word "mimic". Rob Seaman National Optical Astronomy Observatory
Re: Consensus rather than compromise
In message <[EMAIL PROTECTED]>, Rob Seaman writes: >Yes, I assert that we already agree on what I'm saying - or trying to >say here. Let's put aside six years of squabbling about details and >look at the larger picture. > >John Cowan and others on the "leap seconds suck" side of the >discussion have often said things that indicate that, whatever the >tolerance, there is some common sense connection between darkness and >the concept of midnight: > >>> "as long as the clock doesn't say noon when it's midnight" But apart from a select little crew of time-nuts and the geographically gifted, nobody has UTC on their clock: They have local time which is some number of minutes offset from UTC. We could replace UTC with TAI, or kill leapseconds in UTC and let it keep its offset from TAI or do a myriad of other things and still keep "the clock" as people see it on their wrist [1] in sufficient sync with the light of day through minor acts of timezone adjustments. If you want to get me to agree with you on something resembling the statement you made, then it is this: Local Legal/Civilian time will probably always have the sun highest in the sky somewhere around 12:00 through political modification of timezone affiliation. It follows trivially from there that it doesn't matter a dingos fetid kidneys [2] to legal/civilian time what UTC does with relation to the Sun, as long as it is not something ridiculous as monthly leapseconds. Poul-Henning [1] VCR's will probably still flash "12:00AM" though. [2] Yes, I just saw the movie :-) -- 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: Consensus rather than compromise
[B]ut we already agree on a common position that civil time needs to mimic solar time for most purposes. Kashi, Kashi, Kashi. My apologies - I appear not to be making my point clear (again). Communication is hard - email communication between individuals who have never met face-to-face, all the harder. I do question, however, the success of a rhetorical gambit of chanting the name of a breakfast cereal :-) It's interesting that no matter how much we keep telling him otherwise, Rob still claims that "we already agree" on the above statement. Yes, I assert that we already agree on what I'm saying - or trying to say here. Let's put aside six years of squabbling about details and look at the larger picture. John Cowan and others on the "leap seconds suck" side of the discussion have often said things that indicate that, whatever the tolerance, there is some common sense connection between darkness and the concept of midnight: "as long as the clock doesn't say noon when it's midnight" I merely assert that this is 100% equivalent to my statement. First, implicit in this statement is an assumption that civil time will be continue to be constructed around the concept of a "day". There is no a priori reason that civil time ought not be built around a simple incremental counter like Posix, or that civil time might not be judged to be equivalent to the calendar, or even to some Star Trek stardate gimmick - but I seriously question whether civil time could possibly be ready for such a massive philosophical change for hundreds of years. Second, any standard has to meet a minimum requirement for stability. In the case of civil time, that requirement rests somewhere between, say, a decade and a millennium. Politicians have a short memory, but it certainly stretches from one year to the next - a day or a month or a year is too short for visible effects to be acceptable to the world's power brokers. On the other hand, we have expended the last six years worrying about millennial scale issues. I ain't talking about those. So assume civil time can get by with a decade scale stability horizon. Over ten years an expression of civil time resembling our familiar ancient sexigesimal notation has to remain, ON AVERAGE, synchronized to daylight hours "as long as the clock doesn't say noon when it's midnight". I also ain't talking about the apparent Sun wandering back and forth across the sky due to Daylight Saving Time or the Equation of Time. What are we talking about for stability? Here is a plot of the length of the "actual apparent" solar day throughout the course of the year: daylength.pdf Description: Adobe PDF document That is, the length of the day is 86400 SI seconds +/- 30s (~15s RMS). This diagram is perhaps less familiar than its time integral, the Equation of Time: Note that daily excursions of tens of seconds accumulate as annual excursions of tens of minutes. But, as I've said over and over again, leap seconds are a secular effect, not a periodic effect as illustrated above. Even just a one second difference between the length of the civil day and the length of the mean solar day will accumulate to a one hour shift over the course of a decade - day-by- day, tiny monotonic epsilons add up. So, yes, I assert that a one hour slip of civil time versus solar time is far too large to tolerate over the course of a decade. That being the case, it follows, like night follows day, that civil time must mimic mean solar time to better (likely much better) than one second per day. That's all I was trying to say in the previous message. Rob Seaman National Optical Astronomy Observatory
Re: Consensus rather than compromise
In message: <[EMAIL PROTECTED]> "Poul-Henning Kamp" <[EMAIL PROTECTED]> writes: : In message <[EMAIL PROTECTED]>, Peter Bunclark writes: : : >I would have thought that part of the answer to the difficulty in : >implementation and testing would be to use an open-source library of tried : >and tested algorithms. I don't quite understand why software engineers : >seem to feel the need to write new leap-second handling code every time : >they invent a new gadget. : : The vast majority of software engineers do use standard code, they : use their operating systems libraries, this makes them seemingly : leap second compliant. : : "Seemingly" here covers that they are only compliant in all the : seconds that are not leapseconds or seconds right before leap : seconds. : : The POSIX definition makes it impossible to correctly handle leap : seconds with any complying implementation of the standard, and : therefore applications which needs to be *truly* leapsecond compliant, : cannot use the standard libraries. Not to mention devices that handle leap seconds almost, but not entirely, correctly. Much of the fancy footwork that I've had to do is because some devices are better than others at their pedantic compliance. If one relies on just one detail that's gotten wrong, then one's downstream data will be wrong. Knowing what one can trust and not trust, as well as building in the cross checks is also very device specific. This motorola receiver gets this datum wrong, but that datum right, while this other motorola receiver gets it the other way round. This other GPS receiver supplies data that sounds like it should be the same as the reliable motorola data, but in fact is something subtly different. The problems generally aren't in the leap second ticking code (which is in the kernel and has been proven correct through repeated testing). The problems are in getting experience with the actual details of how a specific device (and sometimes the specific firmware) operates. The problems are in what optimizations one can make to recover time faster from a cold start than waiting for the leap info to arrive at some random time in the next 1/2 hour. The problems are in what the power off behaviors of devices are. The problems can even be in how one tests the leap seconds in a simulator because some devices have a strong notion that time flows forward only and produce bad data for a while when that notion is violated. All these details are hard to enshrine in a write once, reuse forever open source (or even closed source) library. Warner
Re: Consensus rather than compromise
In message <[EMAIL PROTECTED]>, Peter Bunclark writes: >> The POSIX definition makes it impossible to correctly handle leap >> seconds with any complying implementation of the standard, and >> therefore applications which needs to be *truly* leapsecond compliant, >> cannot use the standard libraries. >> >So we need just one other, published, open, correctly implemented, and >tested library and all your problems go away. No, because all sorts of governments and companies mandate "POSIX compliance" so you couldn't sell the resulting product. -- 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: Consensus rather than compromise
On Tue, 30 Aug 2005, Poul-Henning Kamp wrote: > In message <[EMAIL PROTECTED]>, Peter Bunclark writes: > > >I would have thought that part of the answer to the difficulty in > >implementation and testing would be to use an open-source library of tried > >and tested algorithms. I don't quite understand why software engineers > >seem to feel the need to write new leap-second handling code every time > >they invent a new gadget. > > The vast majority of software engineers do use standard code, they > use their operating systems libraries, this makes them seemingly > leap second compliant. > > "Seemingly" here covers that they are only compliant in all the > seconds that are not leapseconds or seconds right before leap > seconds. > > The POSIX definition makes it impossible to correctly handle leap > seconds with any complying implementation of the standard, and > therefore applications which needs to be *truly* leapsecond compliant, > cannot use the standard libraries. > So we need just one other, published, open, correctly implemented, and tested library and all your problems go away. Peter.
Re: Consensus rather than compromise
In message <[EMAIL PROTECTED]>, Peter Bunclark writes: >I would have thought that part of the answer to the difficulty in >implementation and testing would be to use an open-source library of tried >and tested algorithms. I don't quite understand why software engineers >seem to feel the need to write new leap-second handling code every time >they invent a new gadget. The vast majority of software engineers do use standard code, they use their operating systems libraries, this makes them seemingly leap second compliant. "Seemingly" here covers that they are only compliant in all the seconds that are not leapseconds or seconds right before leap seconds. The POSIX definition makes it impossible to correctly handle leap seconds with any complying implementation of the standard, and therefore applications which needs to be *truly* leapsecond compliant, cannot use the standard libraries. -- 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: Consensus rather than compromise
On Tue, 30 Aug 2005, M. Warner Losh wrote: > > Leap seconds cost actual companies lots of $$$. I know that I've > personally put in about 50 hours to leap second issues since July 1, > and others in my company have put in even more in testing, shipping > equiptment to the simulator facility, writing simulation software for > testing all our products that couldn't be shipped to the simulation > facility, etc. While it is the cost of doing business, implementing > and conforming to this standard is expensive. > > Warner > Part of the previous traffic in this interminable argument is that hard figures are lacking for both the implementation of leap seconds and for their demise. I would have thought that part of the answer to the difficulty in implementation and testing would be to use an open-source library of tried and tested algorithms. I don't quite understand why software engineers seem to feel the need to write new leap-second handling code every time they invent a new gadget. Peter.
Re: Consensus rather than compromise
In message: <[EMAIL PROTECTED]> "Poul-Henning Kamp" <[EMAIL PROTECTED]> writes: : In message <[EMAIL PROTECTED]>, "John.Cowan" writes: : >Rob Seaman scripsit: : : >> [B]ut we already agree on a common : >> position that civil time needs to mimic solar time for most purposes. : > : >Kashi, Kashi, Kashi. : : It's interesting that no matter how much we keep telling him : otherwise, Rob still claims that "we already agree" on the above : statement. The tolerance most people have is on the order of an hour or two, not sub-second measurements at some purely arbitrary meridian. Timezones are an artificial construct, but have created this tolerance in people. I think that any future time standard should recognize this reality and not be artificially constrained by astronomical measurements at some meridian. Leap seconds cost actual companies lots of $$$. I know that I've personally put in about 50 hours to leap second issues since July 1, and others in my company have put in even more in testing, shipping equiptment to the simulator facility, writing simulation software for testing all our products that couldn't be shipped to the simulation facility, etc. While it is the cost of doing business, implementing and conforming to this standard is expensive. Warner
Re: Consensus rather than compromise
In message <[EMAIL PROTECTED]>, "John.Cowan" writes: >Rob Seaman scripsit: >> [B]ut we already agree on a common >> position that civil time needs to mimic solar time for most purposes. > >Kashi, Kashi, Kashi. It's interesting that no matter how much we keep telling him otherwise, Rob still claims that "we already agree" on the above statement. -- 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: Consensus rather than compromise
Rob Seaman scripsit: > Folks keep mentioning Indiana as a special case. What makes Indiana a special case is that it has seven different sets of time-zone rules, and that's only true if you ignore variations prior to the Epoch (1970-01-01T00:00:00Z). 1) Gibson, Jasper, Lake, LaPorte, Newton, Porter, Posey, Spencer, Vandenburgh, and Warrick counties are in the Central Time Zone and observe DST accordingly. 2) Dearborn and Ohio counties are in the Eastern Time Zone and observe DST accordingly. 3) Clark, Floyd, and Harrison counties are in the Eastern Time Zone, except that they did not observe DST in 1974. 4) Part of Crawford county was in the Eastern Time Zone (except for not observing DST in 1974) until 1976; now it is in the Indiana Time Zone. 5) Starke county was in the Central Time Zone until 1991; it is now in the Indiana Time Zone. 6) Switzerland county was in the Eastern Time Zone until 1973; it is now in the Indiana Time Zone. 7) The remaining 74 counties are in the unofficial Indiana Time Zone; that is, they are in the Eastern Time Zone but do not observe DST. As of the next DST transition in April 2006, the entire state will be on DST; however, the exact details of which counties will be Eastern and which Central have not yet been worked out. > Again, this confuses secular effects with periodic effects. Even the > most extreme "nuke the leap second" position that has been expressed > has assumed that civil time corresponds to a high level of precision > with solar time. I have repeatedly expressed my position that LMT is a matter for specialists, and that as long as the clock doesn't say noon when it's midnight, most casual users of LCT will not care at all how large the discrepancy is (especially given that it's now 2h56m in Kashi). All this can be achieved easily and in accordance with subsidiarity, by fixing the world's time on TAI (or something with a constant offset) and leaving it to local jurisdictions to change their timezone offsets as needed to cope with uncomfortably large LMT - LCT. > [B]ut we already agree on a common > position that civil time needs to mimic solar time for most purposes. Kashi, Kashi, Kashi. -- Overhead, without any fuss, the stars were going out. --Arthur C. Clarke, "The Nine Billion Names of God" John Cowan <[EMAIL PROTECTED]>
Re: Consensus rather than compromise
On Aug 29, 2005, at 2:12 PM, Clive D.W. Feather wrote: And, by the way, the "GMT standard" is *NOT* synonymous with UTC; it is (IIRC) UT1. The original UTC standard (i.e., CCIR 460-4) stated: "GMT may be regarded as the general equivalent of UT." UT1 and UTC are both representations of Universal Time. In a world with one-hour wide time zones, the idea of a leap hour is equivalent to the deprecation of the idea of Universal Time. I suggest that fiddling with the hourly shifts will continue every few years ad nauseam, so one more reason for doing so won't bother anyone. Folks keep mentioning Indiana as a special case. More than one- fourth (13) of the states are cut by time zone boundaries: http:// geography.about.com/library/misc/ntimezones.htm One asserts that UTC, GMT and the standard time zone system are precisely what allows local governments the flexibility to make such decisions for themselves. The whole point of DST (in its modern context) is to conserve energy: DST exists precisely because an hour's difference in the time of sunrise can be valued as a large economic factor. Contrast this with a well-formed consensus - several disagreeing factions are locked in a room until they all agree on a common vision of how to proceed. That works when it works. Not when there are irreconcilable differences in the "general requirements and objectives". It would be hard to characterize the squabbling over the last few years as irreconcilable differences. We haven't even succeeded in getting an appropriate selection of the affected parties assembled either online or face-to-face. Would love to see a well advertised UTC workshop organized in DC (or Orlando, for that matter). It would be delightful if folks were to arrive with an open mind, as well; only one option has ever been considered. We may be in the process of shooting that single option down, but that doesn't mean we can't identify a consensus position around some other proposal. Time is on our side. What is needed is civil time to continue to reflect solar time as it has since literally the dawn of time. Within a couple of hours plus or minus. Again, this confuses secular effects with periodic effects. Even the most extreme "nuke the leap second" position that has been expressed has assumed that civil time corresponds to a high level of precision with solar time. A proposal to identify civil time with TAI (or TAI plus some constant) is only being entertained because the SI second approximates 1/86400 of a mean solar day to a few milliseconds per day. I happen to think those milliseconds matter a lot - others think they don't matter at all - but we already agree on a common position that civil time needs to mimic solar time for most purposes. We should be willing to consider alternatives that are quite different from the status quo. That is the intent of the decision tree that has been posted. But do any of us really expect that we will end up with a civil time standard corresponding to an 18 hour day? Or even with a civil day that corresponds to the actual sidereal period of the spinning Earth, 86164 SI seconds? Rather, I think we all expect that any civil time standard that is viable over the next few centuries will correspond very closely to the mean solar day length. (And I'm doubtful that any of us would want to live on a planet or in a society for which this assertion was false :-) With no sense of irony - thanks for the excellent discussion. Rob Seaman National Optical Astronomy Observatory
Re: Consensus rather than compromise
Rob Seaman said: >> The problem here is Microsoft, whose software appears to believe >> that the current LCT here is "GMT Daylight Time". > > The case has been repeatedly made that since the world tolerates > large excursions in civil time such as caused by the varying local > Daylight Saving Time policies, and by these policies changing, sometimes on short notice, yes. > that the world's institutions and > populace will be able to simply ignore leap hours on those rare > occasions when they are needed. What is offered up is evidence for > the exact opposite. False. > We're shown that Daylight Saving has been > mishandled in a trivially simple instance and that the GMT standard, > synonymous with UTC, is capable of misinterpretation (by minions of > the richest man on Earth) completely distinct from leap second > related issues. No, it appears that a few people think that "the GMT standard" is synonymous with UK local time. This is just as much a fallacy as the belief that Indiana currently observes US "Central Time". And, by the way, the "GMT standard" is *NOT* synonymous with UTC; it is (IIRC) UT1. > Nothing about the ITU proposal would mitigate the > situation being discussed. True. Nor would it mitigate the Indiana problem. Nor, incidentally, would it harm either. > It would be the constant daily persistence of a large DUT1 > that would make leap hours unpalatable Why? Apart from astronomers, of course, who actually cares what the value of DUT1 is? Consider the value DLCT (LCT-UTC). This varies between -1 and 3601 over the year, yet the only effect it has is that it varies whether or not I have to turn on the car headlights on the way to work. > And if > civilians are surprised by the requirements of civil time now, how > much more so they will be in a world in which the last leap hour > troubled their great-great-...-great-grandparents? Yet they cope with the complex proposals to move counties of Indiana between zones, or to move DST end-dates every decade or so. We coped with the introduction of British Standard Time and its abolition. I suggest that fiddling with the hourly shifts will continue every few years ad nauseam, so one more reason for doing so won't bother anyone. > Contrast > this with a well-formed consensus - several disagreeing factions are > locked in a room until they all agree on a common vision of how to > proceed. Call this the "Twelve Angry Men" effect. That one faction > or another may have to completely change their original position is a > strength, not a weakness. Ideally none of the factions even arrives > in the room with a specific position to bargain over, but rather > arrives only with general requirements and objectives. That works when it works. Not when there are irreconcilable differences in the "general requirements and objectives". > What is needed is civil time to continue to reflect solar time as it > has since literally the dawn of time. Within a couple of hours plus or minus. -- Clive D.W. Feather | Work: <[EMAIL PROTECTED]> | Tel:+44 20 8495 6138 Internet Expert | Home: <[EMAIL PROTECTED]> | Fax:+44 870 051 9937 Demon Internet | WWW: http://www.davros.org | Mobile: +44 7973 377646 Thus plc||
Re: Consensus rather than compromise
In message <[EMAIL PROTECTED]>, "Clive D.W. Feather " writes: >[1] Microsoft has been known to get this wrong as well, attempting to apply >US rules to the EU. For once I'll defend Microsoft and say that they probably merely tried to be UNIX compatible here. Many years ago I ended up writing a small program which hunted down all binaries on the system, located the libc time functions if they were linked in (no shlibs back then), and patched up the DST code to implement EU rules. The scary part was that we had to send this hack to all customers because the vendor, Zilog in this particular case, only promised to fix it in the next release. I don't think it was generally gotten right until Olivetti fell into the SVR.4 trap. -- 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: Consensus rather than compromise
John.Cowan said: >> Rather, the very definition of >> civil time was misunderstood, whether by Microsoft or by somebody >> else. > I think this greatly overstates the case. Exactly. > There was a mere misapplication > of labels involved, both in the case of the conference leader (who believes > that the name "GMT" refers to the LCT of the U.K.) Which is a relatively rare belief, easily countered by (for example) looking at the BBC news web site. > and the anonymous Microsoft > programmer (who believes that British Summer Time should be called > "GMT Daylight Time"). Exactly. The belief that the "T" means Time, therefore it's subject to DST. I wonder if it mishandles zones near the equator which don't have DST? Neither are to do with the *definition* of civil time [1], but with its name. [1] Microsoft has been known to get this wrong as well, attempting to apply US rules to the EU. -- Clive D.W. Feather | Work: <[EMAIL PROTECTED]> | Tel:+44 20 8495 6138 Internet Expert | Home: <[EMAIL PROTECTED]> | Fax:+44 870 051 9937 Demon Internet | WWW: http://www.davros.org | Mobile: +44 7973 377646 Thus plc||
Re: Consensus rather than compromise
Rob Seaman scripsit: > I did find it striking, however, that the public confusion being > discussed was completely unconnected to issues of precision > timekeeping such as leap seconds. Rather, the very definition of > civil time was misunderstood, whether by Microsoft or by somebody > else. I think this greatly overstates the case. There was a mere misapplication of labels involved, both in the case of the conference leader (who believes that the name "GMT" refers to the LCT of the U.K.) and the anonymous Microsoft programmer (who believes that British Summer Time should be called "GMT Daylight Time"). -- With techies, I've generally found John Cowan If your arguments lose the first round http://www.reutershealth.com Make it rhyme, make it scan http://www.ccil.org/~cowan Then you generally can [EMAIL PROTECTED] Make the same stupid point seem profound! --Jonathan Robie
Re: Consensus rather than compromise
On Aug 29, 2005, at 10:36 AM, Poul-Henning Kamp wrote: I thought you were busy with your analysis document ? Let's see...rummage, rummage...what did I say? Ah, yes: I'm going to refrain from commenting on the "best" choices from the decision tree until it nears completion. I don't see that I've violated that intent. I stated that consensus was better than artificial compromise. And my message acknowledged that socially pragmatic choices such as you advocate might indeed be appropriate - if in service of appropriate ends. I doubt it came as a surprise to anyone that I still support the notion that civil time should be a representation - of some sort - of solar time. Nowhere in that message did I advocate one solution over another of how to bring this about. I did find it striking, however, that the public confusion being discussed was completely unconnected to issues of precision timekeeping such as leap seconds. Rather, the very definition of civil time was misunderstood, whether by Microsoft or by somebody else. If the solution to the perceived problem of leap seconds is to eradicate them, is the solution to the problem of confusion caused by Daylight Saving Time to convince the politicians to vote against it? We'd have more luck legislating against the transfer of angular momentum from the Earth to the Moon... Rob Seaman National Optical Astronomy Observatory
Re: Consensus rather than compromise
In message <[EMAIL PROTECTED]>, Rob Seaman writes: >Poul-Henning Kamp wrote: > >> It is not unrelated to why some of us think that changing the >> definition of UTC is infinitely more possible than changing the >> rest of the worlds educational level with regards to timekeeping. > >Not unrelated, simply completely irrelevant. Your argument, >apparently shared by the folks pushing the ITU proposal, is not >without merit. Folks don't understand civil time issues now and we >have little hope they ever will, so why not take the purely pragmatic >action of redefining UTC? The failure of your argument is not that >public policy in an imperfect world sometimes requires compromise. >The failure is that the compromise being offered doesn't address the >problem at hand. I thought you were busy with your analysis document ? -- 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.
Consensus rather than compromise
Poul-Henning Kamp wrote: It is not unrelated to why some of us think that changing the definition of UTC is infinitely more possible than changing the rest of the worlds educational level with regards to timekeeping. Not unrelated, simply completely irrelevant. Your argument, apparently shared by the folks pushing the ITU proposal, is not without merit. Folks don't understand civil time issues now and we have little hope they ever will, so why not take the purely pragmatic action of redefining UTC? The failure of your argument is not that public policy in an imperfect world sometimes requires compromise. The failure is that the compromise being offered doesn't address the problem at hand. Clive D.W. Feather wrote: The problem here is Microsoft, whose software appears to believe that the current LCT here is "GMT Daylight Time". The case has been repeatedly made that since the world tolerates large excursions in civil time such as caused by the varying local Daylight Saving Time policies, that the world's institutions and populace will be able to simply ignore leap hours on those rare occasions when they are needed. What is offered up is evidence for the exact opposite. We're shown that Daylight Saving has been mishandled in a trivially simple instance and that the GMT standard, synonymous with UTC, is capable of misinterpretation (by minions of the richest man on Earth) completely distinct from leap second related issues. Nothing about the ITU proposal would mitigate the situation being discussed. And in fact, the analogy between DST and leap hours is faulty. TV's talking heads carefully remind us twice a year either to spring forward or to fall back. DST is a periodic effect. Leap seconds - or leap hours - are secular effects. DUT1 builds up to a high water mark and then the total is transferred to the list of historical leap seconds. It would be the constant daily persistence of a large DUT1 that would make leap hours unpalatable - not only the large corrections that would be needed every few hundred years. And if civilians are surprised by the requirements of civil time now, how much more so they will be in a world in which the last leap hour troubled their great-great-...-great-grandparents? The current DST and leap second standards are much more balanced where it counts - society's talking heads remind the populace twice a year about DST and roughly once every two years about leap seconds. This is just about right from the point of view of reaching the widest possible audience of civilians. The reality is that we don't need - and shouldn't desire - a compromise that will wholly satisfy nobody. What we need - and what we should all desire - is rather a consensus that leads to joint actions supported by all affected communities. Compromise is a symptom of terminating a discussion too soon. The two sides (or more than two sides) are still separated by a gulf of disagreements. Averaging the two positions - or worse yet, having one side trample the other's - cannot possibly produce the optimum solution. Contrast this with a well-formed consensus - several disagreeing factions are locked in a room until they all agree on a common vision of how to proceed. Call this the "Twelve Angry Men" effect. That one faction or another may have to completely change their original position is a strength, not a weakness. Ideally none of the factions even arrives in the room with a specific position to bargain over, but rather arrives only with general requirements and objectives. What is needed is civil time to continue to reflect solar time as it has since literally the dawn of time. Our policies, standards, mechanisms and procedures for making this happen have changed several times throughout history. It is unsurprising that they would need to change again. We would be more productive if we focussed first on the transport mechanisms and procedures that we foresee will be necessary to support third millennium civil time and only later return to the specifics of the standard(s) that will be transported and the policies that those standards will implement. Rob Seaman National Optical Astronomy Observatory
