December 2017 - tz - lists.iana.org

Complexities of time rendered graphically
by Steve Jones Dec. 19, 2017

Dec. 19, 2017

Folks: Today's XKCD comic is amusing: https://xkcd.com/1930/ Steve Jones [image: Emacs!]

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default value of TZDEFAULT
by scs＠eskimo.com Dec. 18, 2017

Dec. 18, 2017

[This is a tzcode issue, not tzdata. Your regular discussion of zone definition and naming issues will resume shortly. :-) ] Consider this simple little program: #include <stdio.h> #include <time.h> int main() { time_t t = time(NULL); struct tm *tmp = localtime(&t); puts(asctime(tmp)); return 0; } There's nothing special about this program (that's the point). But suppose I download tzcode or tzdb and then compile the little program (call it lt.c) along with a just-built localtime(), like this: make localtime.o cc -o lt lt.c localtime.o But if I then run 'lt', it is likely not to work -- there's a pretty good chance it will print the current time in UTC, not my local time zone. If it fails, one reason is that it didn't successfully find my system's already-installed tz files. (That is, I made no attempt to build or install any new tz files.) The reason it didn't find them is obvious enough, and the Makefile contains all the hints I need: TOPDIR= /usr/local # "Compiled" time zone information is placed in the "TZDIR" directory # (and subdirectories). # Use an absolute path name for TZDIR unless you're just testing the software. # TZDIR_BASENAME should not contain "/" and should not be ".", ".." or empty. TZDIR_BASENAME= zoneinfo TZDIR= $(TOPDIR)/etc/$(TZDIR_BASENAME) And, sure enough, on my system, the already-installed tz files are not in /usr/local, they're in /usr/share. So it looks like if I change TOPDIR to /usr/share, or TZDIR to /usr/share/zoneinfo, I should be able to fix it. But no! It still doesn't work, and the reason is, my user environment doesn't have the TZ environment variable set; I'm assuming that the system's default time zone will be used. And, out of the box, the tzcode distribution assumes that the local time zone is defined by a file 'localtime' *in TZDIR*; that is, it essentially assumes that TZDEFAULT is $TZDIR/localtime. But some (perhaps even many) systems put it in /etc/localtime. That's where my (MacOS) system puts it, and a lot of Linux systems put it there, too. The upshot is that on such a system, if you compile and use localtime.c straight out of the tzcode distribution, it won't find your localtime file, and will end up falling back to UTC unless TZ is set. Since the Makefile already lets you set your own version of TZDIR (overriding the setting in tzfile.h), I think it makes sense to do the same thing for TZDEFAULT. Patch attached. With this patch in place, and with the Makefile edited to say TZDEFAULT = "/etc/localtime" fresh compiles of localtime.o correctly find my system's localtime file, and the lt program finally prints local time, as expected. (This tweak to TZDEFAULT's usage helps the extraction case -- that is, when the code tries to fetch the default zone, but not necessarily the tz file building case. I'm not sure whether 'make install' will do the right thing when TZDEFAULT is set, but it definitely doesn't do the right thing if DESTDIR and TZDEFAULT are both set. Is using DESTDIR supported? The Makefile should probably document it if so.) Diagnosing problems involving misconfigured TZDIR and TZDEFAULT variables can be surprisingly difficult. The localtime code doesn't have any way of telling you it's having trouble finding tz files in general, or the localtime file in particular. I'll address that issue in a separate thread. Steve Summit scs(a)eskimo.com

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setting TZ and calling localtime_r
by scs＠eskimo.com Dec. 18, 2017

Dec. 18, 2017

There's code in tzcode (and, I suspect not coincidentally, glibc's localtime implementation as well) to not call the internal version of tzset on calls to localtime_r, but rather only on calls to localtime. The justification is that Posix says localtime_r doesn't need to update the global tzname variable. I don't have a copy of the Posix spec handy, so I can't check: does Posix also say that localtime_r doesn't need to check for and make use of a possibly-changed value of TZ? As implemented (both in tzcode and glibc), it doesn't. If a program calls localtime, then calls setenv to set a new value of TZ, then calls localtime again, it works as expected, but if it calls localtime_r, setenv, localtime_r, it doesn't. (The workaround, of course, is to call localtime_r, setenv, tzset, localtime_r.)

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Kyiv
by gocdoms gocdoms Dec. 18, 2017

Dec. 18, 2017

Hello! City Kyiv is not Kiev. The *founder* of Kyiv is *Kyi*. Not Kie! Please see attached picture.

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Asia/Shanghai (was: Re: Kyiv)
by Phake Nick Dec. 15, 2017

Dec. 15, 2017

Speaking of which, after reading naming convention of zones, wouldn't it still be better to rename the zone to Asia/Beijing mowadays? As almost all users are referring to the zone as "Beijing Time", if in any case there are different time standard emerge that caused Beijing and Shamghai to use different tome standard instead, then it would be more likely for the zone's user to think the Beijing time is a time being continued while Shanghai time would be another new time. In order to reflect the line of thinking and thus when future communication or ammendment easier when things really do change, would such renaming make sense? 2017年12月16日 03:20 於 "Garrett Wollman" <wollman(a)csail.mit.edu> 寫道： > > Contrast the case (which thankfully we do not have to deal with) of > the capital city of the People's Republic of China. In English, it > used to be called "Peking", and in fact in the name of the university > and of the duck dish it still is. The PRC government made a concerted > campaign to change the name used by English speakers to be "Beijing", > which is a phonetic representation of the name of the city in Mandarin > (putonghua). This has to a very large extent worked, and now most > English texts say "Beijing" and not "Peking" (although many people > still don't pronounce it "correctly" because the letters in hanyu > pinyin don't have the same sound values as they do in English). > However, in many languages *other than English*, the name of the city > has not changed -- AFAIK it's still "Pékin" in French, for example.

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tzdata gpg key
by Zura Kutchava Dec. 8, 2017

Dec. 8, 2017

Dear Friends, On https://data.iana.org/time-zones/releases/ I found packages and signatures, but cannot find gpg key to veryfing them. Can you be so kind to tell me where is gpg key for verifying? I am building linux from scratch and writing script for downloading and verifying main packages, so your help will be very important. Thanks beforehand, Regards.

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Europe/Kiev
by Bohdan Vovchuk Dec. 7, 2017

Dec. 7, 2017

Hello. Please change timezone *Europe/Kiev* to *Europe/Kyiv* because first variation is wrong. Ukrainian timezone should be changed to Europe/Kyiv. Kyiv - is a one and only correct international transliteration. -- *Regards, Bohdan Vovchuk*

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Filling the gaps ...
by Lester Caine Dec. 5, 2017

Dec. 5, 2017

The main problem that everybody seems to be skirting around is that the tz database has NO interest in exactly where someone is located and there is no remit TO manage that. Even tzdist which was the latest attempt to plug a major distribution hole has no remit on supplying the correct data for a particular location! Both are simply managing the set of rules that anybody can use where ever they are. Importantly allowing third parts to work out a local time for some elsewhere in the world. Some other data source is really needed to serve up the CURRENT set of rules for a location, and that is probably only currently possible using geonames.org which uses the current timezone_id and it's own simplified timeZone.txt table! What is missing is any historic (or ongoing) changes to that information, such as a location that was using one tz rule set but moved to another. In addition any pre-1970 material can not be identified. tzdist has the remit and tools to fill one of the holes that tz on it's own can not and that is historic changes TO the rule sets. My interest in the tz database came from a major problem with material that had been normalised to UTC time but there was no record as to what rules had been used TO normalise the data, so one could not verify if the CURRENT tz rules were appropriate for establishing the then local times. As Paul has quite rightly pointed out, much historic data was invented, so CORRECTING the data when more accurate information is established is perfectly correct, but one needs to be able to also establish just which rules have changed and one can then adjust the material that is now suspect ( - IF APPROPRIATE ;) ) The whole point of tzdist was to sort current day problems, so if a mobile device with a stored calendar lands in a new location where there has been an 'unscheduled' change of tz rules that change CAN be propagated quickly without needing a full tz update but that will only work if someone is actually running the primary tzdist source. Moving forward, that primary tzdist source needs to maintain a full historic record prior to 1970 since it also provides the base from which rules for historic data normalization can be managed. It allows for the tz timezone_id's to be used to identify the base rule sets, but allows new rule sets to be created ... just without any rules on just how THAT is managed :( Potentially any geonameid could have it's own individual tzdist dataset and track the history of changes as a location moves from one political jurisdiction to another and show it's simple solar time as appropriate. Something that neither tzdist or tz is actually mandated to supply? Merging geonames.org with openstreetmap.org one gets graphic displays of the area that timezones CURRENTLY cover, but one can not establish if the same offsets applied back in the 1960's when DST local times are well documented. And both databases throw away the historic data to those mappings along with a whole load of other historic material. While the vast majority of users probably could not care less, the annoyance here is that the material existed so it's not as if we are asking for extra work, just a mechanism that remembers that say in 2014 the Crimea moved from one set of tz rules to another. Once the mechanism is in place, then as new historic material comes to light, the historic record can be corrected and tzdist has the mechanism for that in relation to timezone rules. So as a start ... what has happened to tzdist. The full historic record of tz changes can provide a complete set of data that has been used over the last 20 years and as new changes are logged in now they can be pushed to tzdist while also maintaining tz distribution for off-line population systems. -- 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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[PROPOSED] Pacify GCC 7.2.1 x86-64 -Wmaybe-uninitialized
by Paul Eggert Dec. 4, 2017

Dec. 4, 2017

* zdump.c (main): Add an INITIALIZE to pacify gcc 7.2.1 20170915 (Red Hat 7.2.1-2) on x86-64 with -Wmaybe-uninitialized, which otherwise incorrectly warns that ‘ab’ might be used uninitialized. Clarify the expression that confused GCC (though the clarification is evidently not enough). --- zdump.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/zdump.c b/zdump.c index 3cd4f42..60a027e 100644 --- a/zdump.c +++ b/zdump.c @@ -552,6 +552,7 @@ main(int argc, char *argv[]) } if (t < cutlotime) t = cutlotime; + INITIALIZE (ab); tm_ok = my_localtime_rz(tz, &t, &tm) != NULL; if (tm_ok) { ab = saveabbr(&abbrev, &abbrevsize, &tm); @@ -567,11 +568,10 @@ main(int argc, char *argv[]) : cuthitime); struct tm *newtmp = localtime_rz(tz, &newt, &newtm); bool newtm_ok = newtmp != NULL; - if (! (tm_ok & newtm_ok - ? (delta(&newtm, &tm) == newt - t - && newtm.tm_isdst == tm.tm_isdst - && strcmp(abbr(&newtm), ab) == 0) - : tm_ok == newtm_ok)) { + if (tm_ok != newtm_ok + || (tm_ok && (delta(&newtm, &tm) != newt - t + || newtm.tm_isdst != tm.tm_isdst + || strcmp(abbr(&newtm), ab) != 0))) { newt = hunt(tz, argv[i], t, newt); newtmp = localtime_rz(tz, &newt, &newtm); newtm_ok = newtmp != NULL; -- 2.14.3

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Very cool app that uses yout TZ Database
by Anton Skorniakov Dec. 3, 2017

Dec. 3, 2017

Hello! First of all, I want to thank you very much for such cool time zones database, we are using it in our product. I want to suggest adding one more cool and simple free web based time zone converter app https://timezoneconverterapp.com/ to this page https://data.iana.org/time-zones/tz-link.html (“Web sites using recent versions of the tz database” section). I am one of the creators of this app and of course, it uses IANA TZ Database. Thank you! _________________ Anton

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