September 2014 - tz - lists.iana.org

Time, Clock, and Calendar Programming In C, by Eric S. Raymond
by random832＠fastmail.us Sept. 30, 2014

Sept. 30, 2014

Eric S. Raymond has written an article about the history of the time.h functions at http://www.catb.org/esr/time-programming/ >From his blog post announcing it (http://esr.ibiblio.org/?p=6311) > The C/UNIX library support for time and calendar programming is a nasty mess of historical contingency. I have grown tired of having to re-learn its quirks every time I’ve had to deal with it, so I’m doing something about that. > > Announcing Time, Clock, and Calendar Programming In C, a document which attempts to chart the historical clutter (so you can ignore it once you know why it’s there) and explain the mysteries. > > What I’ve released is an 0.9 beta version. My hope is that it will rapidly attract some thoroughgoing reviews so I can release a 1.0 in a week or so. More than that, I would welcome a subject matter expert as a collaborator. When I saw it I thought it might be generally interesting to people who subscribe to this list.

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Mehdi Ashrafi
by Mehdi Ashrafi Sept. 29, 2014

Sept. 29, 2014

+989376266654

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(FYI) egypt
by Sebastien WILLEMIJNS Sept. 27, 2014

Sept. 27, 2014

http://journalmetro.com/monde/564625/legypte-change-encore-dheure/ i think you know that....

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[tz-announce] 2014h release of tz code and data available
by Paul Eggert Sept. 26, 2014

Sept. 26, 2014

The 2014h release of the tz code and data is available. It reflects the following changes, which were either circulated on the tz mailing list or are relatively minor technical or administrative changes: Changes affecting past time stamps America/Jamaica's 1974 spring-forward transition was Jan. 6, not Apr. 28. Shanks says Asia/Novokuznetsk switched from LMT (not "NMT") on 1924-05-01, not 1920-01-06. The old entry was based on a misinterpretation of Shanks. Some more zones have been turned into links, when they differed from existing zones only for older time stamps. As usual, these changes affect UTC offsets in pre-1970 time stamps only. Their old contents have been moved to the 'backzone' file. The affected zones are: Africa/Blantyre, Africa/Bujumbura, Africa/Gaborone, Africa/Harare, Africa/Kigali, Africa/Lubumbashi, Africa/Lusaka, Africa/Maseru, and Africa/Mbabane. Changes affecting code zdump -V and -v now output gmtoff= values on all platforms, not merely on platforms defining TM_GMTOFF. The tz library's localtime and mktime functions now set tzname to a value appropriate for the requested time stamp, and zdump now uses this on platforms not defining TM_ZONE, fixing a 2014g regression. (Thanks to Tim Parenti for reporting the problem.) The tz library no longer sets tzname if localtime or mktime fails. zdump -c no longer mishandles transitions near year boundaries. (Thanks to Tim Parenti for reporting the problem.) An access to uninitalized data has been fixed. (Thanks to Jörg Richter for reporting the problem.) When THREAD_SAFE is defined, the code ports to the C11 memory model. A memory leak has been fixed if ALL_STATE and THREAD_SAFE are defined and two threads race to initialize data used by gmtime-like functions. (Thanks to Andy Heninger for reporting the problems.) Changes affecting build procedure 'make check' now checks better for properly-sorted data. Changes affecting documentation and commentary zdump's gmtoff=N output is now documented, and its isdst=D output is now documented to possibly output D values other than 0 or 1. zdump -c's treatment of years is now documented to use the Gregorian calendar and Universal Time without leap seconds, and its behavior at cutoff boundaries is now documented better. (Thanks to Arthur David Olson and Tim Parenti for reporting the problems.) Programs are now documented to use the proleptic Gregorian calendar. (Thanks to Alan Barrett for the suggestion.) Fractional-second GMT offsets have been documented for civil time in 19th-century Chennai, Jakarta, and New York. Here are links to the release files: ftp://ftp.iana.org/tz/releases/tzcode2014h.tar.gz ftp://ftp.iana.org/tz/releases/tzdata2014h.tar.gz The files are also available via HTTP as follows: http://www.iana.org/time-zones/repository/releases/tzcode2014h.tar.gz http://www.iana.org/time-zones/repository/releases/tzdata2014h.tar.gz Each release file has a GPG signature, which can be retrieved by appending ".asc" to the above URLs. Copies of these signatures are appended to this message. As usual, links to the latest release files are here: http://www.iana.org/time-zones/repository/tzcode-latest.tar.gz http://www.iana.org/time-zones/repository/tzdata-latest.tar.gz ftp://ftp.iana.org/tz/tzcode-latest.tar.gz ftp://ftp.iana.org/tz/tzdata-latest.tar.gz This release corresponds to commit 651d4deba49e90dd42141bf00dd5e94024100038 dated Thu Sep 25 18:59:03 2014 -0700 and tagged '2014h' in the experimental github repository at <https://github.com/eggert/tz>. Here are the GPG checksums for the release files: -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAABAgAGBQJUJMkaAAoJEO2X6Q5iqn40/xgP/05GMYGaGlB0SdREMb3Tcl37 ofHu8wIlw/zYPqRQsNJX02G0JMm9Ymsxk58K12DrzQvDragun1WEZFYB3qNJjE7c tGd//0NhVUxoGjxQLjrZ6JDr/AlM56iondkbvVzU+2t7mNrNjABg73Ub750fuSzM qt3tpr/+Ba+fOLcKb9uZQqlt6Bc5qAMGXcsBBT0KVeybLjDobaD66yb6kfZ81uNj g3u60H1JKhEe5NduovMLm5NLRtHa4VJCxJki5pwuYgNtuuG9XYpz2vzQ2DuChO8K hjPzR6MpF/KsICAeAsgf+Z6FqDG8LBy39DeyZCwjP9pDPu3VekuW0dpe3Jad/eTC lQB5dubGPkqS6dW1CepoU/Oojdh9CUmlLYIZDCadpE7RfOFqTLLMnEzhVIv2Iluw 5ssTJ0YTomA8XfdVFHoxdZ/woEYg32KF6ssYOOt8+M4xNLNc0zpjLnnwbfpZN1bN SOGnSWkogssPh60Otd60Zy1mx9KnOQAvzQHHMlqRJTCxnVqvLwP2LaUZaYP2nkuo 7WLqGFIjfCc2iIckogkkPotTVNsTuc+FSV6Ck/GMTEHRZrAX34u/iNr2jik7n85s OjEKWz3WKO8Zo7GOk/w7Ekmnt/UzDLEL4RDB2yxWETI8zTxkzfLmEGT/hFVt2JiG yeg7CpXKQtimBKMnMRXl =DxQr -----END PGP SIGNATURE----- -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAABAgAGBQJUJMkaAAoJEO2X6Q5iqn40AcwQAICQe7AszG667Q3EX+jrrvMi np5LQs6UlCJzU+xwpQ0zo8OANPaJRVe11A//j4eWAkZjXGLrpj8GwDNV+AMnPTtB b1UGos9oOitFBsJfXrwRsOUUuMFHUmnIWvIkS6FY3uCG31wXZVUDuRnksUifnB24 Agmz9KI5Be6JHr3d4erzu7rp7gU4FslJ1f4Jvmiy+PnPiMkZJAsf3Lu+O77h/0qR sZNsigf8lXoIakHAQtNiwizk6a1fTAc6VElgk7hwQ9rm1FxiEWWidWv1bF52qbAw kTrdFZEUY5ONe5O8deAf9r3GVKh/3HmMa8Bzf23a8eSDjLrJbhFTb1uZ5P0vRoHu SabrtvhLg8hrUD3RJtEM1rwROaCrdUTfz002DrOX7htA6m9P3af7OmzkWDJ0hlGe EOeAa1YkjcPwGmbYxCWQbexM2KHr4MaIJ1v75lduq1+osEr1dOvzU8/KJzmay59s XWrXXa7ihPyIW+0MCWqTZg8AqTTed9SwMvWRw2gZTM4L23PerfzmM0PzffdY4oCX 9mbCGTKjp+gcMChRJ+Rtf2xlgsHy5uk2tFVCMngL0FW4rm5EIW8R2GhRBrSAkKYb m8KPvc1+ErjK7nkDpFQ1LKk8/H0v08Yk/aYfRmC4IhmJRzB33Ei0ZuWTqU3ilzJ5 743/HDLWaGvpbG639WBU =a4Y0 -----END PGP SIGNATURE----- _______________________________________________ tz-announce mailing list tz-announce(a)iana.org https://mm.icann.org/mailman/listinfo/tz-announce

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tz database
by Zhang, Heather Sept. 24, 2014

Sept. 24, 2014

Hi, I downloaded most recent tz data from http://www.iana.org/time-zones, Time Zone Data v. 2014g (Released 2014-08-28) tzdata2014g.tar.gz<http://www.iana.org/time-zones/repository/releases/tzdata2014g.tar.gz> (278.2kb) Time Zone Code v. 2014g (Released 2014-08-28) tzcode2014g.tar.gz<http://www.iana.org/time-zones/repository/releases/tzcode2014g.tar.gz> (174.0kb) After reading the README file and other document, I understand that the gz is for compiling into unix commands that provide various timezone functions, am I correct? If I m correct, does IANA provide a csv/xls download of tz with daylight saving time info for all cities in the world and delta download periodically? Thanks & Regards, Heather Zhang | Sabre | W: 682.605.2968 | B1 Flex

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[PROPOSED_PATCH] * localtime.c (localtime_tzset): Coalesce two identical flag args.
by Paul Eggert Sept. 23, 2014

Sept. 23, 2014

All callers changed. --- localtime.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/localtime.c b/localtime.c index 30b5fbc..e692513 100644 --- a/localtime.c +++ b/localtime.c @@ -1389,14 +1389,14 @@ localtime_rz(struct state *sp, time_t const *timep, struct tm *tmp) #endif static struct tm * -localtime_tzset(time_t const *timep, struct tm *tmp, bool settz, bool setname) +localtime_tzset(time_t const *timep, struct tm *tmp, bool setname) { int err = lock(); if (err) { errno = err; return NULL; } - if (settz || !lcl_is_set) + if (setname || !lcl_is_set) tzset_unlocked(); tmp = localsub(lclptr, timep, setname, tmp); unlock(); @@ -1406,13 +1406,13 @@ localtime_tzset(time_t const *timep, struct tm *tmp, bool settz, bool setname) struct tm * localtime(const time_t *const timep) { - return localtime_tzset(timep, &tm, true, true); + return localtime_tzset(timep, &tm, true); } struct tm * localtime_r(const time_t *const timep, struct tm *tmp) { - return localtime_tzset(timep, tmp, false, false); + return localtime_tzset(timep, tmp, false); } /* -- 1.9.1

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[PROPOSED PATCH] * northamerica (America/Jamaica): 1974 sprang forward on Jan. 6,
by Paul Eggert Sept. 23, 2014

Sept. 23, 2014

not Apr. 28. * NEWS: Document this. --- NEWS | 2 ++ northamerica | 13 ++++++++++++- 2 files changed, 14 insertions(+), 1 deletion(-) diff --git a/NEWS b/NEWS index 06e7094..8562fae 100644 --- a/NEWS +++ b/NEWS @@ -4,6 +4,8 @@ Unreleased, experimental changes Changes affecting past time stamps + America/Jamaica's 1974 spring-forward transition was Jan. 6, not Apr. 28. + Shanks says Asia/Novokuznetsk switched from LMT (not "NMT") on 1924-05-01, not 1920-01-06. The old entry was based on a misinterpretation of Shanks. diff --git a/northamerica b/northamerica index 0f5ed3c..3d72505 100644 --- a/northamerica +++ b/northamerica @@ -2991,10 +2991,21 @@ Zone America/Tegucigalpa -5:48:52 - LMT 1921 Apr # 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. +# +# Shanks & Pottenger give April 28 for the 1974 spring-forward transition, but +# Lance Neita writes that Prime Minister Michael Manley decreed it January 5. +# Assume Neita meant Jan 6 02:00, the same as the US. Neita also writes that +# Manley's supporters associated this act with Manley's nickname "Joshua" +# (recall that in the Bible the sun stood still at Joshua's request), +# and with the Rod of Correction which Manley said he had received from +# Haile Selassie, Emperor of Ethiopia. See: +# Neita L. The politician in all of us. Jamaica Observer 2014-09-20 +# http://www.jamaicaobserver.com/columns/The-politician-in-all-of-us_17573647 +# # Zone NAME GMTOFF RULES FORMAT [UNTIL] 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 - EST 1974 -5:00 US E%sT 1984 -5:00 - EST -- 1.9.3

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Chile 2014 changes
by DONATELLA SABELLICO Sept. 22, 2014

Sept. 22, 2014

Hi, in which "Time Zone Data " are contained the Chile 2014 changes? See http://www.minenergia.cl/ministerio/noticias/generales/ministerio-de-energi… Donatella Sabellico. "One Life. One Love. To love each other" Visit IBM TWA Forum! https://ibm.biz/BdxJFs TWA NewsLetter! http://ibm.biz/Bdxij4 Join SMC Connect community! https://www.ibm.com/developerworks/servicemanagement/ IBM Italia S.p.A. Sede Legale: Circonvallazione Idroscalo - 20090 Segrate (MI) Cap. Soc. euro 347.256.998,80 C. F. e Reg. Imprese MI 01442240030 - Partita IVA 10914660153 Società con unico azionista Società soggetta all?attività di direzione e coordinamento di International Business Machines Corporation (Salvo che sia diversamente indicato sopra / Unless stated otherwise above)

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[PROPOSED PATCH 1/4] Have zdump output gmtoff= even on platforms lacking TM_GMTOFF.
by Paul Eggert Sept. 22, 2014

Sept. 22, 2014

* zdump.c (adjusted_yday, gmtoff): New functions. (show): Use new function gmtoff to output gmtoff= even on platforms that do not define TM_GMTOFF. * NEWS: Document this. --- NEWS | 3 +++ zdump.c | 49 ++++++++++++++++++++++++++++++++++++++++++------- 2 files changed, 45 insertions(+), 7 deletions(-) diff --git a/NEWS b/NEWS index 21e85a7..618ddb7 100644 --- a/NEWS +++ b/NEWS @@ -17,6 +17,9 @@ Unreleased, experimental changes Changes affecting code + zdump -V and -v now output gmtoff= values on all platforms, + not merely on platforms defining TM_GMTOFF. + The tz library's localtime and mktime functions now set tzname to a value appropriate for the requested time stamp, and zdump now uses this on platforms not defining TM_ZONE, fixing a 2014g regression. diff --git a/zdump.c b/zdump.c index 0aa94fc..92dd3c1 100644 --- a/zdump.c +++ b/zdump.c @@ -851,19 +851,54 @@ delta(struct tm * newp, struct tm *oldp) return result; } +/* Return A->tm_yday, adjusted to compare it fairly to B->tm_yday. + Assume A and B differ by at most one year. */ +static int +adjusted_yday(struct tm const *a, struct tm const *b) +{ + int yday = a->tm_yday; + if (b->tm_year < a->tm_year) + yday += 365 + isleap_sum(b->tm_year, TM_YEAR_BASE); + return yday; +} + +/* If A is the broken-down local time and B the broken-down UTC for + the same instant, return A's UTC offset in seconds, where positive + offsets are east of Greenwich. On failure, return LONG_MIN. */ +static long +gmtoff(struct tm const *a, struct tm const *b) +{ +#ifdef TM_GMTOFF + return a->TM_GMTOFF; +#else + if (! b) + return LONG_MIN; + else { + int ayday = adjusted_yday(a, b); + int byday = adjusted_yday(b, a); + int days = ayday - byday; + long hours = a->tm_hour - b->tm_hour + 24 * days; + long minutes = a->tm_min - b->tm_min + 60 * hours; + long seconds = a->tm_sec - b->tm_sec + 60 * minutes; + return seconds; + } +#endif +} + static void show(timezone_t tz, char *zone, time_t t, bool v) { register struct tm * tmp; - struct tm tm; + register struct tm * gmtmp; + struct tm tm, gmtm; printf("%-*s ", longest, zone); if (v) { - tmp = my_gmtime_r(&t, &tm); - if (tmp == NULL) { + gmtmp = my_gmtime_r(&t, &gmtm); + if (gmtmp == NULL) { printf(tformat(), t); } else { - dumptime(tmp); + dumptime(gmtmp); printf(" UT"); } printf(" = "); @@ -874,10 +909,10 @@ show(timezone_t tz, char *zone, time_t t, bool v) if (*abbr(tmp) != '\0') printf(" %s", abbr(tmp)); if (v) { + long off = gmtoff(tmp, gmtmp); printf(" isdst=%d", tmp->tm_isdst); -#ifdef TM_GMTOFF - printf(" gmtoff=%ld", tmp->TM_GMTOFF); -#endif /* defined TM_GMTOFF */ + if (off != LONG_MIN) + printf(" gmtoff=%ld", off); } } printf("\n"); -- 1.9.3

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Thread Safety Notes
by Andy Heninger Sept. 22, 2014

Sept. 22, 2014

I've been looking over the thread safe additions to localtime.c, and have a few comments. 1. Use of C's 'volatile' declaration is not sufficient to implement fully thread-safe double-checked locking. The complications are confusing and subtle. Here is a paper that goes into the question in depth: http://www.aristeia.com/Papers/DDJ_Jul_Aug_2004_revised.pdf The bottom line is that doing it right needs memory barrier operations - a read acquire and write release or equivalent for the flag variable being tested. Volatile does not guarantee these. C11 has the necessary functions, but is not yet widely available. [ http://www.open-std.org/jtc1/sc22/WG14/www/docs/n1570.pdf ] Compilers mostly have non-standard extensions available that will do the job, often modeled after those in gcc. 2. The function gmtcheck() needs to recheck the gmt_is_set flag after acquiring the lock. As it stands, multiple threads could replicate the initialization, overwriting a previously set gmtptr in the process. This is unrelated to the volatile question. 3. The volatile variable lcl_is_set is referenced while not holding the lock in only one place, in localtime_r(). And from there the function localtime_tzset() is unconditionally called, which unconditionally acquires the lock. With minor refactoring, all access to lcl_is_set could be from code that is holding the lock, which would allow lcl_is_set to be an ordinary variable with no special thread safety considerations. If it were up to me, I would probably remove use of the double-checked idiom, and rely on solely lock(). Slightly slower, but simple, portable and safe. The alternative is to #define some compiler-dependent atomic operations. Thanks, -- Andy Heninger

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