[PATCH 1/3] Fix off-by-one bug with Kingston Mean Time.
* northamerica (America/Cayman, America/Jamaica, America/Grand_Turk): Change KMT from -5:07:12 to -5:07:11 (should be -5:07:10.41). * zone.tab: Fine-tune geographical coordinates to match -5:07:10.41. I chose the latitude to match the General Post Office, Kingston, in the city center according to Google Maps. --- northamerica | 19 +++++++------------ zone.tab | 2 +- 2 files changed, 8 insertions(+), 13 deletions(-) diff --git a/northamerica b/northamerica index 3a572ba..55755dd 100644 --- a/northamerica +++ b/northamerica @@ -2622,7 +2622,7 @@ Zone Atlantic/Bermuda -4:19:18 - LMT 1930 Jan 1 2:00 # Hamilton # Cayman Is # Zone NAME GMTOFF RULES FORMAT [UNTIL] Zone America/Cayman -5:25:32 - LMT 1890 # Georgetown - -5:07:12 - KMT 1912 Feb # Kingston Mean Time + -5:07:11 - KMT 1912 Feb # Kingston Mean Time -5:00 - EST # Costa Rica @@ -3067,17 +3067,12 @@ Zone America/Tegucigalpa -5:48:52 - LMT 1921 Apr # Great Swan I ceded by US to Honduras in 1972 # Jamaica - -# From Bob Devine (1988-01-28): -# Follows US rules. - -# From U. S. Naval Observatory (1989-01-19): -# JAMAICA 5 H BEHIND UTC - -# From Shanks & Pottenger: +# Shanks & Pottenger give -5:07:12, but Milne records -5:07:10.41 from an +# unspecified official document, and says "This time is used throughout the +# island". Go with Milne. Round to the nearest second as required by zic. # Zone NAME GMTOFF RULES FORMAT [UNTIL] -Zone America/Jamaica -5:07:12 - LMT 1890 # Kingston - -5:07:12 - KMT 1912 Feb # Kingston Mean Time +Zone America/Jamaica -5:07:11 - LMT 1890 # Kingston + -5:07:11 - KMT 1912 Feb # Kingston Mean Time -5:00 - EST 1974 Apr 28 2:00 -5:00 US E%sT 1984 -5:00 - EST @@ -3217,7 +3212,7 @@ Rule TC 2007 max - Mar Sun>=8 2:00 1:00 D Rule TC 2007 max - Nov Sun>=1 2:00 0 S # Zone NAME GMTOFF RULES FORMAT [UNTIL] Zone America/Grand_Turk -4:44:32 - LMT 1890 - -5:07:12 - KMT 1912 Feb # Kingston Mean Time + -5:07:11 - KMT 1912 Feb # Kingston Mean Time -5:00 TC E%sT # British Virgin Is diff --git a/zone.tab b/zone.tab index 769432b..7d4c575 100644 --- a/zone.tab +++ b/zone.tab @@ -233,7 +233,7 @@ IR +3540+05126 Asia/Tehran IS +6409-02151 Atlantic/Reykjavik IT +4154+01229 Europe/Rome JE +4912-00207 Europe/Jersey -JM +1800-07648 America/Jamaica +JM +175805-0764736 America/Jamaica JO +3157+03556 Asia/Amman JP +353916+1394441 Asia/Tokyo KE -0117+03649 Africa/Nairobi -- 1.8.3.1
* africa (Africa/Juba): Now a link to Africa/Khartoum. --- africa | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/africa b/africa index a92d7f5..9a5d93b 100644 --- a/africa +++ b/africa @@ -1100,9 +1100,7 @@ Zone Africa/Khartoum 2:10:08 - LMT 1931 3:00 - EAT # South Sudan -Zone Africa/Juba 2:06:24 - LMT 1931 - 2:00 Sudan CA%sT 2000 Jan 15 12:00 - 3:00 - EAT +Link Africa/Khartoum Africa/Juba # Swaziland # Zone NAME GMTOFF RULES FORMAT [UNTIL] -- 1.8.3.1
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]
This is more likely to be correct. --- europe | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/europe b/europe index 04f61d9..434a2f1 100644 --- a/europe +++ b/europe @@ -1564,10 +1564,11 @@ Zone Europe/Riga 1:36:24 - LMT 1880 2:00 EU EE%sT # Liechtenstein -# Zone NAME GMTOFF RULES FORMAT [UNTIL] -Zone Europe/Vaduz 0:38:04 - LMT 1894 Jun - 1:00 - CET 1981 - 1:00 EU CE%sT +# From Paul Eggert (2013-09-09): +# Shanks & Pottenger say Vaduz is like Zurich. +# Given the close ties between Liechtenstein and Switzerland during WWII, +# assume our circa-1941 corrections to Zurich apply also to Vaduz. +Link Europe/Zurich Europe/Vaduz # Lithuania -- 1.8.3.1
On Mon, 9 Sep 2013, Paul Eggert wrote:
This is more likely to be correct. --- europe | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/europe b/europe index 04f61d9..434a2f1 100644 --- a/europe +++ b/europe @@ -1564,10 +1564,11 @@ Zone Europe/Riga 1:36:24 - LMT 1880 2:00 EU EE%sT
# Liechtenstein -# Zone NAME GMTOFF RULES FORMAT [UNTIL] -Zone Europe/Vaduz 0:38:04 - LMT 1894 Jun - 1:00 - CET 1981 - 1:00 EU CE%sT +# From Paul Eggert (2013-09-09): +# Shanks & Pottenger say Vaduz is like Zurich. +# Given the close ties between Liechtenstein and Switzerland during WWII, +# assume our circa-1941 corrections to Zurich apply also to Vaduz. +Link Europe/Zurich Europe/Vaduz
This removes LMT etc for Vaduz, resulting in data loss. Please don't remove data. cheers, Derick -- http://derickrethans.nl | http://xdebug.org Like Xdebug? Consider a donation: http://xdebug.org/donate.php twitter: @derickr and @xdebug Posted with an email client that doesn't mangle email: alpine
Derick Rethans <tz@derickrethans.nl> writes:
On Mon, 9 Sep 2013, Paul Eggert wrote:
diff --git a/europe b/europe index 04f61d9..434a2f1 100644 --- a/europe +++ b/europe @@ -1564,10 +1564,11 @@ Zone Europe/Riga 1:36:24 - LMT 1880 2:00 EU EE%sT
# Liechtenstein -# Zone NAME GMTOFF RULES FORMAT [UNTIL] -Zone Europe/Vaduz 0:38:04 - LMT 1894 Jun - 1:00 - CET 1981 - 1:00 EU CE%sT +# From Paul Eggert (2013-09-09): +# Shanks & Pottenger say Vaduz is like Zurich. +# Given the close ties between Liechtenstein and Switzerland during WWII, +# assume our circa-1941 corrections to Zurich apply also to Vaduz. +Link Europe/Zurich Europe/Vaduz
This removes LMT etc for Vaduz, resulting in data loss. Please don't remove data.
I don't believe the four second LMT difference between Vaduz and Zurich is data worth preserving, or is in any sense meaningful in the time period about which we're talking. I agree with this change. -- Russ Allbery (rra@stanford.edu) <http://www.eyrie.org/~eagle/>
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
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. On 2013-09-09 17:00, Clive D.W. Feather wrote:
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.
--
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)?
Guy Harris said:
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?
That's a good question. I suggest the answer is that you need to be able to put a range in there as an alternative to a single date.
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)?
I don't have a good answer to that. For the UK, I'd say that statute and common law trumps usage, so there's a single transition date irrespective of what some people did (the leading law case on the matter was to do with the fact that the courthouse clock used "railway" time rather than LMT). If there is some kind of statutory basis, use that - if it varies across the region, use the range facility I suggest above. If we don't have a good idea when people changed, then we're no worse off than we are right now. -- 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
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/>
Russ Allbery <rra@stanford.edu> writes:
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.
You would think that after having read those rules multiple times and then even pasted them, I would have seen the difference between 34 and 38, but apparently I have the same bug as copiers with JBIG compression. Apologies for that. The LMT difference is, of course, four minutes and four seconds, not four seconds, which is somewhat more relevant than I had thought. -- 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/>
Russ Allbery wrote:
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).
Careful -- it sounds like you're starting to get addicted too.... Your note gave me an excuse to do a bit more research. A problem with that analysis is that it relies on the tz data, which says that all of Switzerland (except Geneva) switched at the same time, which I'm pretty sure is not true. Shanks records it that way, but this is most likely due to a dubious decision to guess the date of the 1848 Swiss constitution as the introduction of almost country-wide standard time, which historically makes little sense -- it's like guessing July 4, 1776 as the date of construction of the White House. My bit of research found that Shanks's guess is almost surely wrong (no surprise there), and I have the following further patch to push. One of these days I'll try to track down Messerli's thesis, as he talks about Zurich quite a bit, according to the Hathi Trust index (which is online even though Messerli's thesis is not). I hope this helps to explain why any distinction between Zurich and Vaduz is not supported by reliable sources, as far as we know. More generally, almost all of the tz database's transitions from LMT to standard time lack reliable sources, and are most likely wrong even in the city they purport to represent and are almost certainly wrong for the region. In that sense, the LMT-to-standard-time transitions are no more reliable or useful than the LMT offsets themselves are, and by themselves should not justify the existence of distinct Zones in the database.
From 147ea0873b6c18c3cd68895d951d0df22bd316c6 Mon Sep 17 00:00:00 2001 From: Paul Eggert <eggert@cs.ucla.edu> Date: Mon, 9 Sep 2013 21:49:20 -0700 Subject: [PATCH] * europe (Europe/Zurich): Move 1848 transition to 1855.
--- europe | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/europe b/europe index 434a2f1..79376b8 100644 --- a/europe +++ b/europe @@ -2661,11 +2661,20 @@ Zone Europe/Stockholm 1:12:12 - LMT 1879 Jan 1 # follow Bern Mean Time but kept its own local mean time. # To represent this, an extra zone would be needed. +# From Paul Eggert (2013-09-09): +# We can find no reliable source for Shanks's claim that all of Switzerland +# except Geneva switched to Bern Mean Time at 00:00 on 1848-09-12. On the +# contrary, a more-reliable source talks about "the gradual introduction of a +# national time (from the 1850s)" (Google translation) with a switch to CET in +# 1894; see Speich's review of Messerli's thesis, Traverse 1997/3, 131-3 +# <http://www.tg.ethz.ch/dokumente/pdf_files/rez_messerli.pdf>. For now, model +# this messy process as a transition in 1855. The "0:29:44" is also suspect. + # Rule NAME FROM TO TYPE IN ON AT SAVE LETTER/S Rule Swiss 1941 1942 - May Mon>=1 1:00 1:00 S Rule Swiss 1941 1942 - Oct Mon>=1 2:00 0 - # Zone NAME GMTOFF RULES FORMAT [UNTIL] -Zone Europe/Zurich 0:34:08 - LMT 1848 Sep 12 +Zone Europe/Zurich 0:34:08 - LMT 1855 # See above comment. 0:29:44 - BMT 1894 Jun # Bern Mean Time 1:00 Swiss CE%sT 1981 1:00 EU CE%sT -- 1.8.3.1
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....)
On 2013-09-09 23:03, Paul Eggert wrote:
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....)
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.
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
Paul, I would no trust this biography quoted below. Astrology has played an important role in Switzerland during the 20th century, and a large number of astrologer's clients were born in the second half of the 19th century, the time period in question. Swiss astrologers were professionally concerned about using correct time, and being Swiss, they took that serious. 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. The exception is Geneva, which was on Geneva mean time during this period. There may be anecdotal evidence that some church clocks handled it differently, but this does not change the fact the Switzerland had a uniform standard time at that period. ------------- By he way, the linking of Vaduz (Liechtenstein) with Zurich is ***historically wrong***. Liechtenstein was on LMT until 1 June 1894. Not on Berne time. It also did not follow Switzerland with daylight saving time in 1941 and 1942. No DST is recorded for Liechtenstein up to 1981, when it introduced it in 1981, a year later than the European Union. My source at hand: Gabriel, Traite de l'heure dans le monde, edition 1991. I have other sources at my office, but will not be there before next week. Regards Alois Treindl Astrodienst, Zollikon Switzerland On 10.09.13 08:40, Paul Eggert wrote:
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
I will research this further. For the moment I can offer from the Historical Lexicon of Switzerland http://www.hls-dhs-dss.ch/index.php this excerpt: Die Gründung des Bundesstaats 1848 brachte keine Vereinheitlichung der Z. Weiterhin richtete sich jede Ortschaft nach ihrer jeweiligen Lokalzeit. Die Zeitdifferenz zwischen dem östlichsten Punkt des Landes im Val Müstair und dem westlichsten im Kt. Genf betrug rund 18 Minuten. Mit dem Aufbau eines Telegrafienetzes ab 1852 wurden die unterschiedl. Lokalzeiten erstmals zum Problem, denn die Beschleunigung der Kommunikation verlangte nach einem einheitl. Zeitsystem. 1853 verfügte der zuständige Bundesrat für den gesamten Post- und Telegrafieverkehr des Landes die mittlere Lokalzeit von Bern als Einheitszeit. Diese wurde ab 1860 täglich vom Observatorium Neuenburg bestimmt und der Telegrafendirektion in Bern zur Verfügung gestellt. Auch der Betrieb der Eisenbahnen richtete sich nach der mittleren Lokalzeit von Bern, die in der 2. Hälfte des 19. Jh. zur fakt. Landeszeit wurde. my translation: The founding of the federal state in 1848 did not bring a unification of time. Each town followed its local time. The time difference between the most eastern points of the country in Val Mustair and the most western point in Canton Geneve was around 18 minutes. With the construction of a telegraph network since 1852, the different local times became a problem, as the acceleration of communication demanded a uniform system of time. 1853 the federal government issued the local time of Bern as standard time for the complete post and telegraph traffic. Since 1860, this time was provided by the Neuenburg observatory on a daily basis to the central telegraph office in Bern. Also the railway traffic followed the uniform local mean time of Bern, which became the effective time of all the country in the second half of the 19th century. ---- So the fact that Bern mean time was the uniform time of all of Switzerland is established, despite anecdotal evidence of deviations. TZ data deals with legal standard time after all, less so with local deviations. The open point remains an exact date of introduction. It seems to have been gradual between 1851 and 1860, in my opinion. It will probably not be possible to establish an exact date, but I will research further. On 10.09.13 19:26, Paul Eggert wrote:
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.
On 10.09.13 23:57, Paul Eggert wrote:
<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.
the essential phrase in that source is: Viele Kantone machten denn auch 1894 von ihrer Kompetenz Gebrauch und führten die mitteleurop. Zeit eigenständig nach z.T. heftigen öffentl. Debatten in ihrem Hoheitsgebiet ein. Seit 1894 richtet sich die Schweiz nach einem einheitl. Zeitsystem. Many cantons (there are 23) made use of their competence in 1894 [[when the federal goverment introduced Central European Time for post, telegraph and railway which were under federal authority]] and introduced Central European Time by their own decision, after partly intense public debates, for their respective area of sovereignty. Since 1894 Switzerland follows a uniform time system. --- end of translation For TZ, this is not relevant, it only wants to know when the city of Zurich went to CET, as the zone Europe/Zurich does not claim to represent all of Switzerland for the period before 1970. So, we may have different acceptance dates for different cantons, but the source above claims that they were all within the year 1894.
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.
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). It'd also be helpful to know what time of day the 1894 transition was; we're currently guessing 00:00. And of course this helps only with the 1894 transition; for the circa-1855 transition we're still at sea. In looking into this I found an old bug report from you that zic.8 disagrees with what's currently in 'europe'; I'll fix this shortly. Sorry about that. http://mm.icann.org/pipermail/tz/2011-August/008722.html
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
Thanks again. I've pushed the following patch to the experimental repository.
From 09f994d25d62ba6027722fb873b0207f37bf496f Mon Sep 17 00:00:00 2001 From: Paul Eggert <eggert@cs.ucla.edu> Date: Wed, 11 Sep 2013 09:17:03 -0700 Subject: [PATCH] * europe, zic.8: Correct Bern Mean Time to 0:29:46.
Reported by Alois Treindl in <http://mm.icann.org/pipermail/tz/2013-September/020139.html>. --- europe | 22 +++++++++++++--------- zic.8 | 17 ++++++++++------- 2 files changed, 23 insertions(+), 16 deletions(-) diff --git a/europe b/europe index 79376b8..8d26b4e 100644 --- a/europe +++ b/europe @@ -2650,32 +2650,36 @@ Zone Europe/Stockholm 1:12:12 - LMT 1879 Jan 1 # The 1940 rules must be deleted. # # One further detail for Switzerland, which is probably out of scope for -# most users of tzdata: -# The zone file -# 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 +# most users of tzdata: The [Europe/Zurich zone] ... # describes all of Switzerland correctly, with the exception of # the Cantone Geneve (Geneva, Genf). Between 1848 and 1894 Geneve did not # follow Bern Mean Time but kept its own local mean time. # To represent this, an extra zone would be needed. +# +# From Alois Treindl (2013-09-11): +# The Federal regulations say +# http://www.admin.ch/opc/de/classified-compilation/20071096/index.html +# ... the meridian for Bern mean time ... is 7 degrees 26'22.50". +# Expressed in time, it is 0h29m45.5s. -# From Paul Eggert (2013-09-09): +# From Paul Eggert (2013-09-11): +# Round to the nearest even second, 0:29:46. +# # We can find no reliable source for Shanks's claim that all of Switzerland # except Geneva switched to Bern Mean Time at 00:00 on 1848-09-12. On the # contrary, a more-reliable source talks about "the gradual introduction of a # national time (from the 1850s)" (Google translation) with a switch to CET in # 1894; see Speich's review of Messerli's thesis, Traverse 1997/3, 131-3 # <http://www.tg.ethz.ch/dokumente/pdf_files/rez_messerli.pdf>. For now, model -# this messy process as a transition in 1855. The "0:29:44" is also suspect. +# this messy process as a transition in 1855. Shanks's 1894 transition is more +# plausible for Zurich but has not been checked. # Rule NAME FROM TO TYPE IN ON AT SAVE LETTER/S Rule Swiss 1941 1942 - May Mon>=1 1:00 1:00 S Rule Swiss 1941 1942 - Oct Mon>=1 2:00 0 - # Zone NAME GMTOFF RULES FORMAT [UNTIL] Zone Europe/Zurich 0:34:08 - LMT 1855 # See above comment. - 0:29:44 - BMT 1894 Jun # Bern Mean Time + 0:29:46 - BMT 1894 Jun # Bern Mean Time 1:00 Swiss CE%sT 1981 1:00 EU CE%sT diff --git a/zic.8 b/zic.8 index b61ebd3..a2374a1 100644 --- a/zic.8 +++ b/zic.8 @@ -466,10 +466,10 @@ Rule EU 1979 1995 - Sep lastSun 1:00u 0 - Rule EU 1981 max - Mar lastSun 1:00u 1:00 S Rule EU 1996 max - Oct lastSun 1:00u 0 - .sp -.ta \w'# Zone\0\0'u +\w'Europe/Zurich\0\0'u +\w'0:34:08\0\0'u +\w'RULES/SAVE\0\0'u +\w'FORMAT\0\0'u -# Zone NAME GMTOFF RULES FORMAT UNTIL +.ta \w'# Zone\0\0'u +\w'Europe/Zurich\0\0'u +\w'GMTOFF\0\0'u +\w'RULES/SAVE\0\0'u +\w'FORMAT\0\0'u +# Zone NAME GMTOFF RULES/SAVE FORMAT UNTIL Zone Europe/Zurich 0:34:08 - LMT 1855 - 0:29:44 - BMT 1894 Jun + 0:29:46 - BMT 1894 Jun 1:00 Swiss CE%sT 1981 1:00 EU CE%sT .sp @@ -478,10 +478,13 @@ Link Europe/Zurich Switzerland .in .fi In this example, the zone is named Europe/Zurich but it has an alias -as Switzerland. Zurich was 34 minutes and 8 seconds west of GMT until -1855-01-01 at 00:00, when the offset changed to 29 minutes and 44 -seconds. After 1894-06-01 at 00:00 Swiss daylight saving rules (defined -with lines beginning with "Rule Swiss") apply, and the GMT offset + +as Switzerland. This example says that Zurich was 34 minutes and 8 +seconds west of UT until 1855-01-01 at 00:00, when the legal offset +was changed to 7\(de\|26\(fm\|22.50\(sd; although this works out to +0:29.45.50, the input format cannot represent fractional seconds so it +is rounded here. After 1894-06-01 at 00:00 Swiss daylight saving rules +(defined with lines beginning with "Rule Swiss") apply, and the UT offset became one hour. From 1981 to the present, EU daylight saving rules have applied, and the UTC offset has remained at one hour. .PP -- 1.8.1.2
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.
Technically, When I visited once, they explained that it is a German (not Swiss) Principality (ie: it has a German prince.). But since Germany is no longer a kingdom, it defaults to being independent. On 2013-09-10 15:02, Wallace, Malcolm 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. 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
It may well make sense to organize what is currently tz commentary into something that is, well, a bit more organized. The format I'm most familiar with is MediaWiki, for what it's worth.
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
Paul Eggert wrote:
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?
Theoretically... we have two types of uncertainty: quantitative ("LMT in Zurich is within 17 seconds of UT+00:34:08") and qualitative ("in 1860 Zurich was probably using Bern Mean Time but we don't have any actual record of that"). (My +/- 17 seconds on LMT is based on an estimate of Zurich's longitudinal extent.) Instead of passing bare numbers back and forth across the API, we'd have an extended version of the API that accepts and returns structured pseudo-number objects that represent the uncertainty. The historical localtime() API itself can't represent the uncertainty, and would likely be reimplemented as a wrapper for the extended API that strips off all the uncertainty tags. Quantitative uncertainty is readily modelled by using interval arithmetic. Instead of any single number you have a structure giving lower and upper bounds. An interval structure represents a quantity that could have any value within the interval. An exact value corresponds to an interval in which the lower and upper bounds are equal. Arithmetic operations on intervals produce interval results; for example, [2, 4] * [3, 5] = [6, 20]. Note that interval arithmetic doesn't obey numerical arithmetic identities. So if you ask to convert 1812-06-18T12:00:00Z to Zurich time, the answer should be an interval structure, [1812-06-18T12:33:51, 1812-06-18T12:34:25], encompassing the local times that Zurich could have for that UT time. Qualitative uncertainty requires a different kind of structure, mainly containing a best-guess value (which might itself be an interval structure representing quantitative uncertainty) and some indicator of the quality of the guess. Arithmetic operations on guesses produce results with the lowest quality of the inputs; for example, {2, probable} * {3, wild-ass guess} = {6, wild-ass guess}. This too doesn't obey numerical arithmetic identities. This kind of structure could be extended to also include secondary possible values ("if it's not BMT then it's probably LMT"). So if you ask to convert 1862-06-18T12:00:00Z to Zurich time, the answer should be a qualitative-uncertainty structure, {1862-06-18T12:29:44, probable}, indicating the level of our confidence that Zurich was using BMT by that date. The case you raise, of Zurich's adoption of BMT, is slightly more complicated than the above examples. You've expressed it in the form of a quantitative uncertainty in a threshold date, but localtime() (even in the extended form that I imagine) doesn't let you directly ask about that threshold. For the questions you can ask through the API, that quantitative uncertainty in the threshold translates into a qualitative uncertainty about which of two offsets applies during the interval of possible thresholds. Maybe how far through the threshold interval we are dictates the confidence level with which we adopt one offset or the other, expressing the confidence level as a numerical probability. But as the process of adopting BMT probably didn't take the form of a flag day, maybe a different arrangement of confidence levels is more appropriate. The extended API would have to be supported by extended tzfiles that represent the uncertainty in the data. The simple way to do this is to directly replace the tzfile's numerical quantities with these interval and uncertainty structures. Then ordinary-looking arithmetic inside the extended localtime() operates on these structures to produce the right uncertain results. I wrote about these issues in my paper for the 2013 Future of UTC conference, the bulk of which sketches out a time-handling API to cleanly handle all the awkward cases. Preprint at <http://www.fysh.org/~zefram/time/prog_on_time_scales.pdf>; uncertainty is discussed from the bottom of page 9 to top of page 12. I must stress, this is at present totally theoretical. That API sketch is a long-term goal, not a near-term programming project. In fact, I've found existing programming environments somewhat inadequate for the job; I think I need to develop a new programming *language* before I can properly tackle it. -zefram
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.
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 ? Or is there another one? -- 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
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/>
participants (13)
-
Alois Treindl -
Brian Inglis -
Clive D.W. Feather -
David Patte ₯ -
Derick Rethans -
Guy Harris -
Lester Caine -
Paul Eggert -
Paul_Koning@Dell.com -
Russ Allbery -
Stephen Colebourne -
Wallace, Malcolm -
Zefram