On 9 September 2013 19:54, Paul Eggert <eggert@cs.ucla.edu> wrote:

* africa (Africa/Juba): Now a link to Africa/Khartoum.

My resolved data indicates that this has no impact as both chanegd from LMT on the same date. Fine by me. Stephen Africa/Juba LMT: +02:06:24 Transition[Overlap at 1931-01-01T00:00+02:06:24 to +02:00] Transition[Gap at 1970-05-01T00:00+02:00 to +03:00] Transition[Overlap at 1970-10-15T00:00+03:00 to +02:00] Transition[Gap at 1971-04-30T00:00+02:00 to +03:00] Transition[Overlap at 1971-10-15T00:00+03:00 to +02:00] Transition[Gap at 1972-04-30T00:00+02:00 to +03:00] Transition[Overlap at 1972-10-15T00:00+03:00 to +02:00] Transition[Gap at 1973-04-29T00:00+02:00 to +03:00] Transition[Overlap at 1973-10-15T00:00+03:00 to +02:00] Transition[Gap at 1974-04-28T00:00+02:00 to +03:00] Transition[Overlap at 1974-10-15T00:00+03:00 to +02:00] Transition[Gap at 1975-04-27T00:00+02:00 to +03:00] Transition[Overlap at 1975-10-15T00:00+03:00 to +02:00] Transition[Gap at 1976-04-25T00:00+02:00 to +03:00] Transition[Overlap at 1976-10-15T00:00+03:00 to +02:00] Transition[Gap at 1977-04-24T00:00+02:00 to +03:00] Transition[Overlap at 1977-10-15T00:00+03:00 to +02:00] Transition[Gap at 1978-04-30T00:00+02:00 to +03:00] Transition[Overlap at 1978-10-15T00:00+03:00 to +02:00] Transition[Gap at 1979-04-29T00:00+02:00 to +03:00] Transition[Overlap at 1979-10-15T00:00+03:00 to +02:00] Transition[Gap at 1980-04-27T00:00+02:00 to +03:00] Transition[Overlap at 1980-10-15T00:00+03:00 to +02:00] Transition[Gap at 1981-04-26T00:00+02:00 to +03:00] Transition[Overlap at 1981-10-15T00:00+03:00 to +02:00] Transition[Gap at 1982-04-25T00:00+02:00 to +03:00] Transition[Overlap at 1982-10-15T00:00+03:00 to +02:00] Transition[Gap at 1983-04-24T00:00+02:00 to +03:00] Transition[Overlap at 1983-10-15T00:00+03:00 to +02:00] Transition[Gap at 1984-04-29T00:00+02:00 to +03:00] Transition[Overlap at 1984-10-15T00:00+03:00 to +02:00] Transition[Gap at 1985-04-28T00:00+02:00 to +03:00] Transition[Overlap at 1985-10-15T00:00+03:00 to +02:00] Transition[Gap at 2000-01-15T12:00+02:00 to +03:00] Africa/Khartoum LMT: +02:10:08 Transition[Overlap at 1931-01-01T00:00+02:10:08 to +02:00] Transition[Gap at 1970-05-01T00:00+02:00 to +03:00] Transition[Overlap at 1970-10-15T00:00+03:00 to +02:00] Transition[Gap at 1971-04-30T00:00+02:00 to +03:00] Transition[Overlap at 1971-10-15T00:00+03:00 to +02:00] Transition[Gap at 1972-04-30T00:00+02:00 to +03:00] Transition[Overlap at 1972-10-15T00:00+03:00 to +02:00] Transition[Gap at 1973-04-29T00:00+02:00 to +03:00] Transition[Overlap at 1973-10-15T00:00+03:00 to +02:00] Transition[Gap at 1974-04-28T00:00+02:00 to +03:00] Transition[Overlap at 1974-10-15T00:00+03:00 to +02:00] Transition[Gap at 1975-04-27T00:00+02:00 to +03:00] Transition[Overlap at 1975-10-15T00:00+03:00 to +02:00] Transition[Gap at 1976-04-25T00:00+02:00 to +03:00] Transition[Overlap at 1976-10-15T00:00+03:00 to +02:00] Transition[Gap at 1977-04-24T00:00+02:00 to +03:00] Transition[Overlap at 1977-10-15T00:00+03:00 to +02:00] Transition[Gap at 1978-04-30T00:00+02:00 to +03:00] Transition[Overlap at 1978-10-15T00:00+03:00 to +02:00] Transition[Gap at 1979-04-29T00:00+02:00 to +03:00] Transition[Overlap at 1979-10-15T00:00+03:00 to +02:00] Transition[Gap at 1980-04-27T00:00+02:00 to +03:00] Transition[Overlap at 1980-10-15T00:00+03:00 to +02:00] Transition[Gap at 1981-04-26T00:00+02:00 to +03:00] Transition[Overlap at 1981-10-15T00:00+03:00 to +02:00] Transition[Gap at 1982-04-25T00:00+02:00 to +03:00] Transition[Overlap at 1982-10-15T00:00+03:00 to +02:00] Transition[Gap at 1983-04-24T00:00+02:00 to +03:00] Transition[Overlap at 1983-10-15T00:00+03:00 to +02:00] Transition[Gap at 1984-04-29T00:00+02:00 to +03:00] Transition[Overlap at 1984-10-15T00:00+03:00 to +02:00] Transition[Gap at 1985-04-28T00:00+02:00 to +03:00] Transition[Overlap at 1985-10-15T00:00+03:00 to +02:00] Transition[Gap at 2000-01-15T12:00+02:00 to +03:00]

Derick Rethans said:

This removes LMT etc for Vaduz, resulting in data loss. Please don't remove data.

I disagree. The LMT figures are nonsense, since they apply only to a narrow stripe within each zone. I'd like to see them all removed. Rather, we should have markers of when zonal times, as opposed to LMT, first came into effect. For places where we know the legal change point, such as the UK, this is a "happened at" date-time. For places where we don't, it's a "happened sometime before" date-time, and we probably want a way to distinguish these. But don't put LMT values in the files; remove the ones that are there. -- Clive D.W. Feather | If you lie to the compiler, Email: clive@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646

On Sep 9, 2013, at 4:13 PM, David Patte ₯ <dpatte@relativedata.com> wrote:

I actually don't use the LMT value in tz, so I am not personally concerned if it is lost, but I do use the date and time that the city moved from LMT, which would be a shame to lose.

Clive is suggesting losing the LMT values (which are redundant with an indication of the longitude of the city whose name appears in the tzid):

...

The LMT figures are nonsense, since they apply only to a narrow stripe within each zone. I'd like to see them all removed.

and

...

But don't put LMT values in the files; remove the ones that are there.

and suggesting, as you are, *NOT* losing the date and time that the region covered by the tzid went to some form of "standard time" or "zonal time":

...

Rather, we should have markers of when zonal times, as opposed to LMT, first came into effect. For places where we know the legal change point, such as the UK, this is a "happened at" date-time. For places where we don't, it's a "happened sometime before" date-time, and we probably want a way to distinguish these.

Now, whether that's "the city" or "the region covered by the tzid" is another matter; what should we do if a given locale covered by a tzid didn't all adopt (in some sense) zonal time all at once? Use the date and time the city designated by the tzid did? Use the date and time that the last location in that region did? Split the region into multiple regions, each of which adopted zonal time all at once (most of the shiny new tzids for the shiny new regions will presumably disappear if a customer of the tzdb winnows it down)? Also, what sense of "adopt" should we, well, *adopt*? "Adopted by a government for a region that includes all of the region in question" (which needn't always be a national government), or should we include common use (for which it might be more difficult to choose a date and time)?

David Patte ₯ <dpatte@relativedata.com> writes:

I actually don't use the LMT value in tz, so I am not personally concerned if it is lost, but I do use the date and time that the city moved from LMT, which would be a shame to lose.

The time of switch to standardized time was already identical between Europe/Vaduz and Europe/Zurich. However, now that I've looked at this more closely, there is another (earlier) transition that may possibly be of issue for data completionists, which is a new consideration that people have only recently asked the database take into account. Let me help for the people who don't have a copy of the current data readily available. Current (well, 2013d) Europe/Vaduz: Zone Europe/Vaduz 0:38:04 - LMT 1894 Jun 1:00 - CET 1981 1:00 EU CE%sT Europe/Zurich: Zone Europe/Zurich 0:34:08 - LMT 1848 Sep 12 0:29:44 - BMT 1894 Jun # Bern Mean Time 1:00 Swiss CE%sT 1981 1:00 EU CE%sT So the result of this change for Europe/Vaduz is that the DST corrections for Europe/Zurich from 1941 to 1942 would be adopted (which as Paul notes is more likely to be correct than the previous state), the historic LMT offset would change by an irrelevant four seconds, and the times between 1848 and 1894 would track Berne instead of Vaduz/Zurich LMT. All of these changes are either more likely to be accurate than what we had or are trivial to the point of irrelevance except for the last, which does mean a change in abbreviation (LMT -> BMT) between 1848 and 1894, if I'm reading the rules correctly, and a time difference of a somewhat more significant 8 minutes and 20 seconds. In terms of the current scope of the project, there is no reason not to make this a link. In terms of the desire to expand the scope project to keep every piece of historical data as accurate as possible, I think there's some question about the LMT to BMT change. The question is whether Liechtenstein would have done something other than all of Switzerland during that time period (with the exception, noted in comments but not in rules due to being out of scope historically for the database, of Cantone Geneve, which kept LMT rather than Berne Mean Time from 1848 to 1894). I am about as far from an expert in European history as one can possibly get, so I don't know the answer to that question. Wikipedia seems to imply that Liechtenstein was closely aligned with Austria-Hungary up until World War I, whereas Switzerland was an independent state, which makes me a bit dubious that Liechtenstein would have standardized on Berne Mean Time. -- Russ Allbery (rra@stanford.edu) <http://www.eyrie.org/~eagle/>

Here, incidentally, is exactly where it would be nice to be able to link to another entry. Assuming for the sake of argument that we want to retain the current pre-standardized-time behavior for Europe/Vaduz, we could change: Zone Europe/Vaduz 0:38:04 - LMT 1894 Jun 1:00 - CET 1981 1:00 EU CE%sT to: Zone Europe/Vaduz 0:38:04 - LMT 1894 Jun => Europe/Zurich where the "=> Europe/Zurich" syntax (that I just made up, and which doubtless could be made much better) says to apply the rules of that zone for the time period of that rule. If you apply a winnowing threshold after June of 1894, the zone would then just become a link; if you don't, it would be a separate zone but would just mirror Europe/Zurich. You could even potentially allow such a line to have an end date, so that you could directly represent "followed all the rules of another zone during ths time range" without duplicating those rules. Without that, applying the DST corrections from 1941 to 1942 to Europe/Vaduz as well requires copying them from Europe/Zurich, which loses the piece of information that they're not confirmed rules specific for Liechtenstein but rather copied rules from Europe/Zurich under the assumption that they were probably the same. You can put that information back in comments, of course, but it still would be nice to be able to represent it in the data format. -- Russ Allbery (rra@stanford.edu) <http://www.eyrie.org/~eagle/>

Clive D.W. Feather wrote:

don't put LMT values in the files; remove the ones that are there

Unfortunately the underlying interface requires that *some* offset be there, and LMT is more accurate than UTC would be, so there is an argument for keeping it in the database so long as it's understood to be a somewhat-flaky approximation. That being said.... In hindsight perhaps we should have not put LMT in there, and instead designed a data format that allows one to say "undefined" (so presumably localtime fails). The same goes for the transition from LMT to standard time, which is often not reliably known even to the nearest decade (even though the data format requires that it be specified to one-second precision!). But how would that be modeled so that the caller of localtime could find this out? Maybe localtime should return randomish values each time you call it, if the result is not reliably known, sort of like randomized rounding? (I'm mostly kidding here....)

Brian Inglis wrote:

Would time standards have been set from local or national observatories, universities with astronomy departments, or admiralty equivalents, prior to and after standard time?

Sure. The Neuchatel Observatory had that role during the standardization of Swiss time in the 19th century. But there was apparently a nontrivial difference between the time it kept and that of Swiss civil clocks. I've read stories of how one needed to change one's watch several times to walk around a Swiss lake in that era. I just now found more evidence that Zurich did not keep Bern time during the period in question, contra the claims in Shanks. One block from Albert Einsten's old apartment in Bern is the Zytglogge (the "time bell"), Bern's main clock tower. Ann M. Hentschel writes this about it: During the second half of the 19th century, the clocktower had the important task of indicating the local Bernese time. The clockworks, including puppets that revolve on the hour, were renovated in 1904. As early as 1874, the Society of Natural Scientists had recommended that the city modernize its timekeeping system and change over to a dozen public electrically driven clocks. The new telegraph and railway networks had made the introduction of a standard time indispensable. Clocks in Zurich, for example, diverged from Bernese clocks by as much as four and a half minutes. This gives a more-realistic picture of how timekeeping actually worked in Switzerland in the late 19th century. By today's standards it was a real zoo. Even Einstein probably had trouble getting to work on time. My source: Hentschel AM. The physical tourist: peripatetic highlights in Bern. Phys perspect 2005;7(1):107-29 http://dx.doi.org/10.1007/s00016-004-0232-0

Alois Treindl wrote:>

All Swiss timezone history sources in astrology books and data collections maintain that all of Switzerland was legally on Berne time, starting 1851, until the introduction of CET on 1 June 1894.

That disagrees with Shanks and with the tz data, but I suppose we should trust Swiss astrology books over Shanks for Swiss data. Is there a specific astrology-book source for that? Also, exactly when in 1851 was the transition? And what exactly was Berne time's offset from GMT? (Shanks gives two values, which disagree!) Do these Swiss astrology books give sources? For example, if there was an 1851 Swiss federal law, what law was it? Given the information I've seen already, I think it unlikely that all of Switzerland (save Geneva) switched at the same time. I think it more likely that the Neuchatel Observatory established a standard (perhaps with some legal backing) and that various localities adopted the standard one by one.

There may be anecdotal evidence that some church clocks handled it differently

There sure is. Here's another. On May 15, 1905, Albert Einstein moved to the edge of Bern's unified time zone. A neighboring clock tower in Muri kept a different time -- thus helping inspire Einstein to the special theory of relativity. Yes, this is just anecdotal evidence and yes, this was after 1894 so the Muri clock was likely nonstandard, but the point is that circa-1900 civil Swiss timekeeping was not as uniform as modern observers might naively imagine. And the Swiss were the best timekeepers of the day....

My source at hand: Gabriel, Traite de l'heure dans le monde, edition 1991.

Ah, so Gabriel agrees with Shanks for Vaduz. Does Gabriel give sources? If Gabriel was compiled the same way that Shanks was and doesn't give sources, then I'm afraid I wouldn't trust Gabriel much either, as most likely Gabriel is just guessing too. But if there are sources that would be another matter. My source for Einstein: Galison P. Einstein's clocks: the place of time. Critical Inquiry 2000;26(2:)355-89 http://www.jstor.org/stable/1344127

Thanks, that summary agrees with the information I've gleaned: for Zurich Shanks is wrong, and so are the Swiss astrology books. It seems pretty clear that if you asked someone for the time in (say) Zurich in 1855, the answer you'd get would depend on who you were talking to. Legally speaking the local time might have been one thing, but the telegraph and railway time another. But even with that in mind, the transitions in Shanks and in the tz database and in the Swiss astrology books all seem to disagree with any reasonable interpretation of "civil time in Zurich". What a mess, eh? For astrological applications I expect you'd want to know what times the midwives and doctors kept -- that should be more important than railway time per se (not too many babies were born in railway stations....). It may be difficult, though, to find out this info for Zurich, much less for all Switzerland. <http://www.hls-dhs-dss.ch/textes/d/D12813.php> makes it appear that the 1894 transition was not a smooth one either -- I suspect that each canton or locality had to make the legal change on its own, and they didn't change all at the same time, and in that sense the 1894 transition datum is dubious too.

Here I have historical details Canton Bern: http://www.digibern.ch/GKB1789/index3t2.html Geschichte des Kantons Bern seit 1798 (History of the Canton Bern since 1798) DIE EINFÜHRUNG DER MITTELEUROPÄISCHEN ZEIT So besass bis zur Mitte des 19. Jahrhunderts jeder Ort seine eigene Lokalzeit, die sich nach Sonnenauf- und Sonnenuntergang richtete. Zwar passten sich umliegende Dörfer oft grösseren Städten an. Dennoch entstanden Schwierigkeiten für die Fahrpläne. Ein erster Schritt zu ihrer Überwindung geschah kurz nach der Gründung des Bundesstaates durch die Vereinheitlichung der Ortszeiten innerhalb der Schweiz, und zwar setzte sich die Berner Ortszeit im übrigen Lande durch. Ausser in Genf gab es nämlich vorerst nur in Bern eine Sternwarte, die präzise Berechnungen erlaubte. Von 1859 an wurde dann allerdings die genaue Zeit nicht mehr hier ermittelt, sondern im neugegründeten Observatorium von Neuenburg, das sie per Telegraf nach Bern weitermeldete. Da aber weiterhin die Berner Zeit Standardzeit blieb, spürte der Berner diese Änderungen nicht. Bis zur Angleichung der Zeit auch im übrigen Europa und in anderen Erdteilen dauerte es noch fast bis zum Jahrhundertende. Nach internationalen Konferenzen über das System der sogenannten Stundenzonen entschied sich der Bundesrat, in der ganzen Schweiz für alle Verkehrsanstalten die mitteleuropäische Zeit einzuführen, die von der Berner Zeit um ziemlich genau dreissig Minuten abwich. In der Folge erliess der Berner Regierungsrat am 18. Mai 1894 ein Kreisschreiben an die Regierungsstatthalter: Es müsse "zur Vermeidung einer verwirrenden Zweispaltigkeit der Zeitbestimmung [...] diese mitteleuropäische Zeit auch für das bürgerliche und amtliche Leben eingeführt werden", und es sollten "sämtliche öffentlichen Uhren (Kirchenuhren und andere) auf den 1.Juni nächsthin um 30 Minuten vorgerückt werden". --- Translation THE INTRODUCTION OF CENTRAL EUROPEAN TIME Until the middle of the 19th century each town had its own local time, following sunrise and sunset [translator note: the author does apparently not know about the concept of mean time, and that it is derived from meridian crossings]. Villages often adapted to nearby larger towns. But problems arose for transport schedules. A fest step after the founding of the federal state [in 1848] was the unification of local times within Switzerland. Bern local time took priority in the rest of the country. Except for Geneva, only Bern had an astronomical observatory, which allowed precise calculations. From 1859 on the precise time was not any more delivered from there, but from the newly founded observatory in Neuenburg, which sent it by telegraph to Bern. But because this was still Bern standard time, the Bern people felt no difference. It took nearly the end of the century until time was unified in the rest of Europe and other continents. After international conferences about the system of the so called hour zones the federal government decided to introduce for all transport institutions in Switzerland the central European time, which differed by nearly exactly 30 minutes from Bern time. The Bern cantonal government issued on 18 May 1894 a circular to the local functionaries: "To avoid a confusing division of times .. this Central European Time must also be introduced for the civil and official life" and so should "all public clocks (church tower clocks and others) on 1 June moved forward by 30 minutes". ---- end translation For Zürich, I have not yet found a similar document. I will have to go to the central library to get access to the protocols of the Canton government from 1894.

On 11.09.13 10:56, Paul Eggert wrote:

Thanks for looking into that. It confirms that Bern time was not exactly GMT+0:30, though we still don't know what it was; our current value (derived from one of the Shanks values) is probably wrong by a few seconds. It also confirms my suspicion that the 1894 transition was messy, but it suggests that our 1894 transition date of June 1 is correct for Zurich, as my guess is that Zurich was not one of the recalcitrant cantons (though it'd be nice to confirm this).

Shanks gives Bern time meridian as 7°26' which is (because he is never more precise than minutes of arc) as close as he can get to the coordinates of the old Bern observatory, which are also the base point of Swiss country topography (Fundamenalpunkt der Schweizer Landeskoordinaten). The Federal regulations say http://www.admin.ch/opc/de/classified-compilation/20071096/index.html Der Fundamentalpunkt im Meridianzentrum der alten Sternwarte von Bern hat die ellipsoidische Länge l = 7°26'22.50" und die ellipsoidische Breite j = 46°57'08.66". I.e. the meridian for Bern mean time, which was based on this observatory, is 7°26'22.50" Expressed in time, it is 0h29m45.5s

It'd also be helpful to know what time of day the 1894 transition was; we're currently guessing 00:00.

I guess so as well. Lacking other information, it seems sensible to assume a change of time

All Swiss timezone history sources in astrology books and data collections maintain that all of Switzerland was legally on Berne time, starting 1851, until the introduction of CET on 1 June 1894.

But technically, Liechtenstein is not part of Switzerland? This email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please delete all copies and notify the sender immediately. You may wish to refer to the incorporation details of Standard Chartered PLC, Standard Chartered Bank and their subsidiaries at http://www.standardchartered.com/en/incorporation-details.html.

Paul Eggert wrote:

My source:

Hentschel AM. The physical tourist: peripatetic highlights in Bern. Phys perspect 2005;7(1):107-29 http://dx.doi.org/10.1007/s00016-004-0232-0

With much of the 'good information' contained in copyright documents, publishing 'proof' is not going to be practical, but with many new usable documents appearing on line, isn't it about time that there was a more practical method of managing these? I've been creating my own private wiki style archive of the ones I have been finding and am now pulling links and where possible copies of other material for the UK area. My wiki system maintains a history of changes to the pages, and there is a calendar system which allows chronologies to be created. Moving this material to a more easily read and searched archive would remove the need to include the notes in the data files, and also allow the building of a lot more complete record which is currently slipping by after all the good work done on creating the git repository? Paul ... would it not make sense to fork a master copy of the repository from which distributions are assembled, leaving your 'experimental' one for your own investigations. Someone will probably then propose using the git wiki for the documentation, but I'd prefer to avoid that as it is not well suited to some of the cross referencing and processing that the material really needs. So a more independently managed site would be preferable. I'm slowly pulling together the tools to create a mapping system to show the physical layout of zones, and this would dovetail in nicely with the rest of the documentation? -- Lester Caine - G8HFL ----------------------------- Contact - http://lsces.co.uk/wiki/?page=contact L.S.Caine Electronic Services - http://lsces.co.uk EnquirySolve - http://enquirysolve.com/ Model Engineers Digital Workshop - http://medw.co.uk Rainbow Digital Media - http://rainbowdigitalmedia.co.uk

On Sep 10, 2013, at 1:28 AM, Brian Inglis <Brian.Inglis@systematicsw.ab.ca> wrote:

Would time standards have been set from local or national observatories, universities with astronomy departments, or admiralty equivalents, prior to and after standard time? Those institutions are most likely to have been involved in production and use of ephemerides and keeping relevant records.

For purposes of generally used time, observatories etc. may not be the most relevant. As I understand it, in a number of countries the impetus for standard time came from railroads -- whose operations are obviously greatly simplified by such a move. paul

Thanks for that note. These are deepish waters, and you might be interested in recent research on how to represent partial temporal knowledge, often motivated by practical data-mining problems. One place to start would be Ligozat's book Qualitative Spatial and Temporal Reasoning (2012), Wiley-ISTE, ISBN 978-1-84821-252-7. As an aside I should mention that I'm not a fan of interval arithmetic; if done carefully it typically results in intervals so large as to be meaningless, and if done sloppily what's the point? Admittedly I am biased here as Stott Parker and I wrote a paper <http://dx.doi.org/10.1002/spe.637> based on random rounding, a quite-different approach that doesn't require a new programming language. Of course we're way off the deep end here, in terms of any practical change I'd propose for the tz code or data. Still, it's often helpful to stay in shouting range of the researchers.

Lester Caine <lester@lsces.co.uk> writes:

Paul Eggert wrote:

...

-Zone Europe/Vaduz 0:38:04 - LMT 1894 Jun

Ignoring the LMT details being lost ... Isn't this the timezone for ISO3166 LI ?

Yes, but it's not uncommon for those zones to be links when they share the same rules. See, for example, Europe/Mariehamn, which is the timezone for AX, Europe/Ljubljana, which is the timezone for SI, or Europe/Bratislava, which is the timezone for SK. -- Russ Allbery (rra@stanford.edu) <http://www.eyrie.org/~eagle/>