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Question about leap seconds
by random832＠fastmail.us Sept. 12, 2013

Sept. 12, 2013

Two things: Can a transition time ever reasonably fall _on_ a leap second, and can the zic input format represent this case? I am sketching out a design for a new time zone file format, and it occurs to me that it might be a good idea to specify transitions with POSIX timestamps so the data regarding one time zone is independent of whether leap seconds are enabled or not.

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Re: [tz] Using MediaWiki / Wikidata
by Lester Caine Sept. 12, 2013

Sept. 12, 2013

Tobias Conradi wrote: > was: Re: [tz] [PATCH 3/3] * europe (Europe/Vaduz): Now a link to Europe/Zurich. > > On Tue, Sep 10, 2013 at 7:29 PM, Paul Eggert <eggert(a)cs.ucla.edu> wrote: >> 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. > And here is some infrastructure using MediaWiki: > https://en.wikipedia.org/wiki/Category:Tz_database > > E.g. > https://en.wikipedia.org/wiki/Africa/Luanda > https://en.wikipedia.org/wiki/America/Indiana/Indianapolis > https://en.wikipedia.org/wiki/Asia/Novosibirsk > > But there are vandalizing admins around, e.g. Anthony Bradbury: > https://en.wikipedia.org/w/index.php?title=Special:Log&page=Time+in+Africa > > Another option could be to use wikidata, e.g. > Asia/Novosibirsk > https://www.wikidata.org/wiki/Q4806295 > and put evidences and for time offsets there. Personally I have no time for wikipedia since we had a lot of well written material removed in the past because some other editors decided they did not like it. So I have no confidence that any material posted would remain clean or even available. I think that a 'private' wiki is much more appropriate given that what we are going to archive is evidential material? With publicly accessible sandboxes for providing new material. Which is then managed based on it's suitability for inclusion? I could live with mediawiki format, but I much prefer clean html documents using ckeditor. And adding interactive packages is something I don't find particularly easy with those type of systems anyway. Is there somewhere appropriate to host a service Paul? I'm happy to run something on my servers, but I suspect the load may be quite high ;) -- 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

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[PATCH 1/3] Fix off-by-one bug with Kingston Mean Time.
by Paul Eggert Sept. 12, 2013

Sept. 12, 2013

* 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

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Re: [tz] uniform time in Switzerland in second half of 19th century
by Paul Eggert Sept. 12, 2013

Sept. 12, 2013

Pierre-Yves Berger found some documentary evidence of the 1894 transition in Switzerland, and I got my hands on a copy of Messerli's book, which gives more details about the circa-1855 transition. Here's a patch, which I'll push to the experimental repository. As far as data goes, this merely moves the 1855 transition to 1853-07-16. >From 9805c5c4a38750ff0c2345fdcc2a273357153259 Mon Sep 17 00:00:00 2001 From: Paul Eggert <eggert(a)cs.ucla.edu> Date: Wed, 11 Sep 2013 18:28:36 -0700 Subject: [PATCH] * europe, zic.8 (Europe/Zurich): Change transition to 1853-07-16. Explain how I derived this guess from Messerli's book. Also, give better evidence about the 1894 transition, from Pierre-Yves Berger. --- europe | 39 ++++++++++++++++++++++++++++----------- zic.8 | 6 +++--- 2 files changed, 31 insertions(+), 14 deletions(-) diff --git a/europe b/europe index 8d26b4e..e70cfb4 100644 --- a/europe +++ b/europe @@ -2662,23 +2662,40 @@ Zone Europe/Stockholm 1:12:12 - LMT 1879 Jan 1 # ... the meridian for Bern mean time ... is 7 degrees 26'22.50". # Expressed in time, it is 0h29m45.5s. +# From Pierre-Yves Berger (2013-09-11): +# the "Circulaire du conseil federal" (December 11 1893) +# <http://www.amtsdruckschriften.bar.admin.ch/viewOrigDoc.do?id=10071353> ... +# clearly states that the [1894-06-01] change should be done at midnight +# but if no one is present after 11 at night, could be postponed until one +# hour before the beginning of service. + # 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. Shanks's 1894 transition is more -# plausible for Zurich but has not been checked. +# Round BMT to the nearest even second, 0:29:46. +# +# We can find no reliable source for Shanks's assertion that all of Switzerland +# except Geneva switched to Bern Mean Time at 00:00 on 1848-09-12. This book: +# +# Jakob Messerli. Gleichmassig, punktlich, schnell: Zeiteinteilung und +# Zeitgebrauch in der Schweiz im 19. Jahrhundert. Chronos, Zurich 1995, +# ISBN 3-905311-68-2, OCLC 717570797. +# +# suggests that the transition was more gradual, and that the Swiss did not +# agree about civil time during the transition. The timekeeping it gives the +# most detail for is postal and telegraph time: here, federal legislation (the +# "Bundesgesetz uber die Erstellung von elektrischen Telegraphen") passed on +# 1851-11-23, and an official implementation notice was published 1853-07-16 +# (Bundesblatt 1853, Bd. II, S. 859). On p 72 Messerli writes that in +# practice since July 1853 Bernese time was used in "all postal and telegraph +# offices in Switzerland from Geneva to St. Gallen and Basel to Chiasso" +# (Google translation). For now, model this transition as occuring on +# 1853-07-16, though it probably occurred at some other date in Zurich, and +# legal civil time probably changed at still some other transition date. # 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. +Zone Europe/Zurich 0:34:08 - LMT 1853 Jul 16 # See above comment. 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 a2374a1..7ea94c5 100644 --- a/zic.8 +++ b/zic.8 @@ -468,7 +468,7 @@ Rule EU 1996 max - Oct lastSun 1:00u 0 - .sp .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 +Zone Europe/Zurich 0:34:08 - LMT 1853 Jul 16 0:29:46 - BMT 1894 Jun 1:00 Swiss CE%sT 1981 1:00 EU CE%sT @@ -480,9 +480,9 @@ Link Europe/Zurich Switzerland In this example, the zone is named Europe/Zurich but it has an alias 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 +seconds west of UT until 1853-07-16 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 +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 -- 1.8.1.2

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Re: [tz] Getting close to new release: testing, testing, ... [SEC=UNOFFICIAL]
by Timothy Arceri Sept. 12, 2013

Sept. 12, 2013

Will you be including the updates to the Australian Daylight Saving's abbreviations in this release? http://mm.icann.org/pipermail/tz/2013-April/019099.html -----Original Message----- From: tz-bounces(a)iana.org [mailto:tz-bounces@iana.org] On Behalf Of Paul Eggert Sent: Wednesday, 11 September 2013 7:55 PM To: Time zone mailing list Subject: [tz] Getting close to new release: testing, testing, ... We need to release a new version soon, because of Fiji. I did further testing and it appears that the recent changes to add meta-information to the zic output won't fly, because they're incompatible with the GNU C library on Ubuntu 12.04. So we need to rethink that feature. There's no rush to introduce it, so let's omit it from the next release. Also, the -t option recently added to tzselect seems like it will be superseded by the tzwinnow approach, whenever we get that working and stable, so for now I think I'd rather omit this. There are a few other problems found by "make public", mostly links that were in the wrong files. I'll post proposed changes soon. If other people could do some testing that'd be nice. You can run "make public". The output should contain the following diagnostics: warning: "antarctica", line 318: Antarctica/Palmer: pre-2013 clients may mishandle distant timestamps warning: "asia", line 1412: 24:00 not handled by pre-1998 versions of zic warning: "asia", line 2332: 24:00 not handled by pre-1998 versions of zic warning: "asia", line 1026: Asia/Jerusalem: pre-2013 clients may mishandle distant timestamps (rule from "asia", line 1021) warning: "asia", line 1315: Asia/Amman: pre-1994 clients may mishandle distant timestamps warning: "asia", line 2016: Asia/Gaza: pre-2013 clients may mishandle distant timestamps warning: "asia", line 2347: Asia/Hebron: pre-2013 clients may mishandle distant timestamps warning: "australasia", line 269: Pacific/Fiji: pre-2013 clients may mishandle distant timestamps warning: "europe", line 998: America/Godthab: pre-2013 clients may mishandle distant timestamps warning: "southamerica", line 1141: America/Santiago: pre-2013 clients may mishandle distant timestamps warning: "southamerica", line 1313: Pacific/Easter: pre-2013 clients may mishandle distant timestamps along with a very long section that starts as follows, which shows that the tz code is still broken on platforms with unsigned 32-bit time_t (this is a longstanding problem). checking uint32_t zones ... --- tzpublic/int64_t.out 2013-09-11 02:43:50.871343089 -0700 +++ tzpublic/uint32_t.out 2013-09-11 02:43:55.907343185 -0700 @@ -210,278 +210,6 @@ Europe/Andorra Sun Mar 29 01:00:00 2037 UT = Sun Mar 29 03:00:00 2037 CEST isdst=1 Europe/Andorra Sun Oct 25 00:59:59 2037 UT = Sun Oct 25 02:59:59 2037 CEST isdst=1 Europe/Andorra Sun Oct 25 01:00:00 2037 UT = Sun Oct 25 02:00:00 2037 CET isdst=0 -Europe/Andorra Sun Mar 28 00:59:59 2038 UT = Sun Mar 28 01:59:59 2038 CET isdst=0 -Europe/Andorra Sun Mar 28 01:00:00 2038 UT = Sun Mar 28 03:00:00 2038 CEST isdst=1 -Europe/Andorra Sun Oct 31 00:59:59 2038 UT = Sun Oct 31 02:59:59 2038 CEST isdst=1

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POSIX extension check
by Arthur David Olson Sept. 10, 2013

Sept. 10, 2013

It's probably worthwhile to check whether extended POSIX in zic-produced binaries will cause grief when those binaries are used with old versions of localtime.c. If so, one or more of documentation, a zic warning, or a version number bump may be in order. --ado

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a patch for zic.c to allow 'follow rules'
by Alois Treindl Sept. 10, 2013

Sept. 10, 2013

Dear Arthur, I have been preparing a small modification for zic.c which will allow it to understand a 'follow rule' in zone files, like this: # experimental table for Geneva, to test the 'follow' mechanism Zone Europe/Geneva 0:24:37 - LMT 1848 Sep 12 0:24:37 - GET 1894 Jun # Geneva MTime 0 follow Europe/Zurich For test purposes, one can simply insert this zone in the europe file. The feature is helpful in the extension of tzdata to cover complete timezone history. For this purpose, about 1000 additional zone files need to be written, and to be maintained. The process to do so has started in the astrological community, as it needs a complete pre-1970 timezone history. I will not bother you with details. I intend to help creating and maintaining a set of files like 'europe_hist', 'asia_hist' etc which contain the additional zones. The 'follow rule' will allow to keep these extra zone files very small, as usually the additional zones will all have a cross-over moment into a regular tzdata zone. I have for the moment called the modified zic source file zicx.c and prepared a patch file for zic.c to implement the 'follow rule' feature. I have tried to keep the modification very small. Please have a look at the patch, and check for the errors I have probably made. Description of the code: ------------------------ The follow rule must be the last line in a zone, and recursion is not allowed. It is parsed in inzsub() which reacts on GMTOFF = 0 and the word 'follow' in the RULE field. The zone line is stored in zones[] with a special value z_gmtoff = FOLLOW_MARK and the zone_name to follow in field z_rule (which is abused for this purpose). Before the call to outzone() the two sets of zone lines are patched together in a temporary array, so that outzone() and all functions deeper down() need not be modified. Patch ----- --- zic.c 2011-03-09 20:41:27.000000000 +0100 +++ zicx.c 2011-08-25 16:09:04.000000000 +0200 @@ -262,6 +262,17 @@ static int typecnt; #define YR_MAXIMUM 1 #define YR_ONLY 2 +/* +** follow rules, added by Alois Treindl August 2011 +** Zones may end with a line: 0 follow zone_name +** which the parser will represent with FOLLOW_MARK in z_gmtoff, +** and the zone name in z_rule. +** Before the call to outzone() the zone and its follow zone will be +** patched together, so that outzone() sees a regular zone array. +** To keep zone files readable, follow rules cannot be used recursively. +*/ +#define FOLLOW_MARK 999999 + static struct rule * rules; static int nrules; /* number of rules */ @@ -589,7 +600,48 @@ _("%s: More than one -L option specified */ for (j = i + 1; j < nzones && zones[j].z_name == NULL; ++j) continue; - outzone(&zones[i], j - i); + if (zones[j -1].z_gmtoff == FOLLOW_MARK) { + /* copy zone and follow zone into one new array */ + int k,n,m, nrows; + struct zone *xzones, *zp; + nrows = j - i - 1; + zp = &zones[j - 1]; /* line with the follow rule */ + xzones = (struct zone *) (void *) emalloc((int) (nrows * sizeof *xzones)); + for (k = 0; k < nrows; k++) + xzones[k] = zones[i + k]; + /* now find the follow zone in array zones[] */ + for (m = 0; m < nzones; m++) { + if (zones[m].z_name != NULL && strcmp(zp->z_rule, zones[m].z_name) == 0) break; + } + if (m == nzones) { /* error, follow zone not found */ + char *cp; + cp = emalloc(80 + strlen(zp->z_rule) + strlen(zones[i].z_name));; + sprintf(cp, "For zone %s follow zone %s not found, no zonefile created.", zones[i].z_name, zp->z_rule); + eat(zp->z_filename, zp->z_linenum); + error(cp); + ifree(cp); + ifree((void *)xzones); + } + /* now find the next date in the follow zone */ + for (n = m + 1; n < nzones; n++) { + if (zp->z_untiltime < zones[n].z_untiltime) break; + } + /* missing errorcode for case n == nzones, + * assume we are still in same follow zone. + * The follow zone part we need starts at zones[n]. + * Now find where follow zone ends, will be m. + */ + for (m = n; m < nzones && zones[m].z_name == NULL; ++m) + continue; + xzones = (struct zone *) (void *) erealloc((char *) xzones, (int) ((nrows + m - n) * sizeof *xzones)); + for (k = 0; k < m - n; k++) + xzones[nrows + k] = zones[n + k]; + nrows += m - n; + outzone(&xzones[0], nrows); + ifree((void *) xzones); + } else { + outzone(&zones[i], j - i); + } } /* ** Make links. @@ -784,7 +836,7 @@ associate(void) } for (i = 0; i < nzones; ++i) { zp = &zones[i]; - if (zp->z_nrules == 0) { + if (zp->z_nrules == 0 && zp->z_gmtoff != FOLLOW_MARK) { /* ** Maybe we have a local standard time offset. */ @@ -1079,11 +1131,23 @@ const int iscont; return FALSE; } } - z.z_rule = ecpyalloc(fields[i_rule]); - z.z_format = ecpyalloc(fields[i_format]); - if (max_format_len < strlen(z.z_format)) - max_format_len = strlen(z.z_format); - hasuntil = nfields > i_untilyear; + /* check for 0 follow zonename + ** zonename must contain at least one /, and follow must be + * 'follow' or an abbreviation thereof. + */ + if (z.z_gmtoff == 0 && strchr(fields[i_format], '/') != NULL + && itsabbr(fields[i_rule], "follow")) { + z.z_gmtoff = FOLLOW_MARK; + z.z_rule = ecpyalloc(fields[i_format]); + z.z_format = ""; + hasuntil = FALSE; /* no continue of zone now */ + } else { + z.z_rule = ecpyalloc(fields[i_rule]); + z.z_format = ecpyalloc(fields[i_format]); + if (max_format_len < strlen(z.z_format)) + max_format_len = strlen(z.z_format); + hasuntil = nfields > i_untilyear; + } if (hasuntil) { z.z_untilrule.r_filename = filename; z.z_untilrule.r_linenum = linenum;

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DESTDIR patch
by Dr. Volker Zell Sept. 10, 2013

Sept. 10, 2013

Hi Attached a patch which adds DESTDIR support to the Makefile. Ciao Volker

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Fiji daylight savings
by David Wheeler Sept. 9, 2013

Sept. 9, 2013

Hi all, we've just received notice that Fiji will start daylight savings shortly, but this doesn't seem to be represented in tzdata. See link below for details. http://www.fiji.gov.fj/Media-Center/Press-Releases/DAYLIGHT-SAVING-STARTS-O… Cheers, -- David _____________________________ David Wheeler - Lead Engineer david(a)inomial.com p +61 3 9663 3554 WINNER 2013 ACOMMS Awards for Services to Industry - Professional services Telecommunications and Utility Billing, Rating, Policy and Session Management

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Rules for TZ+ database
by Lester Caine Sept. 9, 2013

Sept. 9, 2013

First I'd like to thank Kevin Lyda for taking the time to construct the original tz repository. It is a quite remarkable piece of work. I'm currently looking at a beautifully documented history of the Theory file from the moment Authur created it on 16/2/1987 ... 1987-02-16 in modern money ... The first rule is +* In SVR2, time display in a process is controlled by the environment + variable TZ, which "must be a three-letter time zone name, followed + by a munber representing the difference between local time and + Greenwich Mean Time in hours, followed by an optional three-letter + name for a daylight time zone;" when the optional daylight time zone is + present, "standard U.S.A. Daylight Savings Time conversion is applied." + This means that SVR2 can't deal with other (for example, Australian) + daylight savings time rules, or situations where more than two + time zone abbreviations are used in an area. So it was very much conceived as an 'American' system. Handling other daylight saving offsets or more complex rules was to difficult at that time so ignored. I'll fast forward over the changes which introduced long names to replace the three letter codes, and set up rules about size of population being used to select them. Politics is nothing new and the entire database is an archive of POLITICAL decisions. Until 2001 when a commit was added from a certain Paul Eggert ... +This naming convention is not intended for use by inexperienced users +to select TZ values by themselves (though they can of course examine +and reuse existing settings). Distributors should provide +documentation and/or a simple selection interface that explains the +names; see the 'tzselect' program supplied with this distribution for +one example. And the new rule of + * Uniquely identify every national region where clocks have all + agreed since 1970. This is essential for the intended use: static + clocks keeping local civil time. Does not SPECIFICALLY rule out the gathering of pre 1970 data? It just sets the ground rules for ONE view of the data to be limited. This is about making the data more accessible and was probably the wrong approach even back then. I'll skip the 'frivolity' of adding Mars time in 2004, but it does have relevance to the next step forward. All documented data is valid! http://lsces.org.uk/hg/tz/rev/8a52c38a5f56 is the change that pulls support for specifically 32 bit systems, that note had only JUST been added but is the first reference on scope that I've found? Then finally there is a formal definition of the SCOPE of the database in http://lsces.org.uk/hg/tz/rev/7c18a2e16943 so up until that time data HAS been gathered for the whole of time not just post 1970. I'm more than happy to accept this as the rules for 'TZ' but things have moved on considerably since 1987 and substantially more material is now available and easily accessed to provide insight into all of the documented changes to time standards. So if the 'TZ' distribution is going to ignore that material then we need to set up a 'TZ+' distribution that actively includes all available material. It's not a question it's a statement. Reviewing the Theory file of cause we fall at the first hurdle since the POSIX time format has difficulty coping with some of the intricacies of time management. While encoding a daylight saving change in the time is to be commended, it is only right for a specific period of time. The more accurate approach is purely to identify a 'set of rules' that can be used. This also then automatically covers the provision of leap seconds. What I am saying here is that POSIX is just an implementation detail and while mapping the data to it does require defining, it's not fundamental to the real data. So lets use a standard that is better at handling the modern systems. Obviously I fundamentally disagree with the current scope and that should probably have been disputed in 2011. If one accepts that POSIX is incapable of handling the material, then applying one of it's limitations is also wrong? Since the Calendrical issues section already includes the whole of history, we do have a good base to build on, and are already discussing what 'Universal Time' was prior to 1970. If we can agree that while the validity of some legacy data may be questionably, it is a fact of life that many of these events happened, me just have some uncertainty as to when they happened? I think we can also agree that there is substantial new material which is currently only recorded in notes and which can only enhance the historic record? I'm under no illusion that the problems of manipulating this data into a more usable format is substantial, but it is not impossible. NAMING 'timezones' is the fundamental problem here, and the "This naming convention is not intended for use by inexperienced users" is of fundamental importance here. Mapping rules to usable names is all that is required, so internally in the data we have something suitable for managing the complexity of the problem, while outside a naive user punches in an ISO3166 and gets a timezone suitable for the time frame he is working in. There is a substantial amount of additional history here that could potentially be exposed, such as, for example, ISO3166 codes which have been superseded, or even 'old' TZ names which are now recorded for posterity in archives! The 'backward' file is missing key information on when a particular 'match' was changed, and while dates are not particularly critical, there may be fundamental data provided if one of the legacy names is being reviewed and the CURRENT rule set no longer matches what was being supplied at that time. With hg (or git) I can call up an historic view of backward, and then select a view of the data at that time. Something that one time would have been a substantial amount of work happens in the click of a mouse. DVCS provides a view of the information in a format that relates to how it was entered. That data can be viewed in many other ways if we provide the right tools, that is the key here. 'winnowing' is just one way of manipulating the data, and another would be 'time slicing', providing a snapshot of all the rules active at a particular date. Currently there are a much smaller number of rules active than there were pre-1970, and pre standard time there were an infinite number due to all the different methods of tracking time. During the transition from then until now we have some complex information to map, such as French stations being 5 minutes drift, and UK trains using a different time to the legal system. But if we are looking at times when those rules apply then we need to know that there were differences. There was recorded desention to many summertime changes and this happened in a time where those facts were recorded so that material needs to be made available once it is established. This cuases no end of problems in identifying each area affected, but that's why I brought up the OHM historic mapping. Linking up with that, simple things like historic changes of country names can link us to the appropriate data. This may well require the provision of more than one rule, so that is something that needs handling - with notes if necessary. I've not got as far as I would like and I need to get on, but there is more than enough here already. OK 'TZ' only provides data from 1970 but 'TZ+' would provide all the historic data including the 'TZ' filtered set and additional data within the TZ timeframe. -- 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

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