- tz - lists.iana.org

Principles
by Stephen Colebourne Aug. 29, 2013

Aug. 29, 2013

It seems like there are conflicts in the principles behind the tzdb. Here are my thoughts: What is the tzdb? Generally accepted: - widely used - ubiquitous - reliable - accurate post-1970 - handles changes occurring now More controversial: - IDs used in GUIs (they are whether we like it or not) - IDs have meaning (they do whether we like it or not) - pre-1970 is in-scope (data is there whether we like it or not) - pre-1970 data may not be accurate (users like data, care less about its accuracy) - pre-1970 LMT is accurate for the location in the tzdb ID What do end users expect? (developers and non-developers) - users often pick zones based on raw tzdb ID - users don't know the history of zone rules in their location - users do know that they live in an area that might have special zone rules, eg. Busingen/Navajo - users want minimal cognitive effort, pick it and it works - users don't understand the nuances of a cross-border zone, they just associate with their region What do I expect? - Stability - No deletions of data, except where _proven_ wrong - Additions focussed on today and the future - Historical changes only following research - No new time-zones in the main files unless they differ post-1970 - At least one time-zone ID for each ISO-3166 region - Using all files except backward should meet goals above - Backward file is for deprecations only I don't think that any of this is unreasonable, or different from how the tzdb has previously worked. Stephen

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Namibia Time Change
by Hank W. Aug. 26, 2013

Aug. 26, 2013

Reminder: The annual switch from West Africa Time (UTC+1) to West Africa Summer Time (UTC+2) in Namibia only is scheduled for this coming Sunday, 1 September, at 2 AM WAT (1 AM UTC).

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Unable to get the tz database
by Peddi, Radhika (Radhika) Aug. 24, 2013

Aug. 24, 2013

Hi, This is Radhika from Avaya. When I am trying to get tz database from the link http://www.twinsun.com/tz/tz-link.htm, by using FTP distribution, I am getting Host Not Found error. Please find the attached screen shot for the same. When I am using below shell command on my linux setup wget 'ftp://elsie.nci.nih.gov/pub/tz*.tar.gz', I am getting below error --2013-08-20 03:14:03-- ftp://elsie.nci.nih.gov/pub/tz*.tar.gz => `.listing' Resolving elsie.nci.nih.gov... failed: Name or service not known. wget: unable to resolve host address `elsie.nci.nih.gov' Could you please help me how to get rid of this problem. Thanks & Regards, Radhika Peddi|Avaya India Pvt. Ltd.| Wing 'A', Level -5, Tower-11, Cybercity, Magarpatta City, Hadapsar | Pune, 411028|India Voice +91 20 4101 8311| Email: rpeddi<mailto:rpeddi@avaya.com>@avaya.com [ Please consider the environment before printing this email ]

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infinite loop in time2sub
by enh Aug. 22, 2013

Aug. 22, 2013

i recently upgraded Android's copy of tzcode to be closer to tzcode2013d. with Android's signed 32-bit time_t i'm seeing a change in behavior for out-of-range dates. previously given something like this, mktime would return an error, but now it hangs in the binary search in time2sub. struct tm t; memset(&t, 0, sizeof(tm)); t.tm_year = 200; t.tm_mon = 2; t.tm_mday = 10; changing the if (t == lo) { ++t; if (t <= lo) return WRONG; ++lo; } else if (t == hi) { --t; if (t >= hi) return WRONG; --hi; } back to if (t == lo) { if (t == TIME_T_MAX) return WRONG; ++t; ++lo; } else if (t == hi) { if (t == TIME_T_MIN) return WRONG; --t; --hi; } fixes things. looking at the git history in https://github.com/eggert/tz.gitit looks like the old code, found in Android up to and including jb-mr2 (but no longer in AOSP ToT), was never in upstream tzcode. here's where the upstream tzcode's overflow checks were introduced: commit 46fa7e98177cae664f673c6034c9ac74d0ccd0ec Author: Arthur David Olson <olsona@elsie> Date: Tue Aug 9 09:55:06 2005 -0400 overflow work SCCS-file: localtime.c SCCS-SID: 7.96 diff --git a/localtime.c b/localtime.c index 1c3e9b0..d3edb5a 100644 --- a/localtime.c +++ b/localtime.c @@ -1616,9 +1616,13 @@ const int do_norm_secs; if (dir != 0) { if (t == lo) { ++t; + if (t <= lo) + return WRONG; ++lo; } else if (t == hi) { --t; + if (t >= hi) + return WRONG; --hi; } if (lo > hi) looking at the Android AOSP git history, it looks like we found and fixed this bug years ago but never talked to upstream about it: commit 2093d350be21ff086f9e145404877941b9a42c5c Author: David 'Digit' Turner <digit(a)google.com> Date: Wed Sep 9 17:41:59 2009 -0700 Fix an infinite loop in time2sub. The problem is that time_t is signed, and the original code relied on the fact that (X + c < X) in case of overflow for c >= 0. Unfortunately, this condition is only guaranteed by the standard for unsigned arithmetic, and the gcc 4.4.0 optimizer did completely remove the corresponding test from the code. This resulted in a missing boundary check, and an infinite loop. The problem is solved by testing explicitely for TIME_T_MIN and TIME_T_MAX in the loop that uses this. Also fix increment_overflow and long_increment_overflow which were buggy for exactly the same reasons. Note: a similar fix is needed for system/core/libcutils diff --git a/libc/tzcode/localtime.c b/libc/tzcode/localtime.c index 9c5f218..83c1011 100644 --- a/libc/tzcode/localtime.c +++ b/libc/tzcode/localtime.c @@ -75,6 +75,31 @@ static __inline__ void _tzUnlock(void) pthread_mutex_unlock(&_tzMutex); } +/* Complex computations to determine the min/max of time_t depending + * on TYPE_BIT / TYPE_SIGNED / TYPE_INTEGRAL. + * These macros cannot be used in pre-processor directives, so we + * let the C compiler do the work, which makes things a bit funky. + */ +static const time_t TIME_T_MAX = + TYPE_INTEGRAL(time_t) ? + ( TYPE_SIGNED(time_t) ? + ~((time_t)1 << (TYPE_BIT(time_t)-1)) + : + ~(time_t)0 + ) + : /* if time_t is a floating point number */ + ( sizeof(time_t) > sizeof(float) ? (time_t)DBL_MAX : (time_t)FLT_MAX ); + +static const time_t TIME_T_MIN = + TYPE_INTEGRAL(time_t) ? + ( TYPE_SIGNED(time_t) ? + ((time_t)1 << (TYPE_BIT(time_t)-1)) + : + 0 + ) + : + ( sizeof(time_t) > sizeof(float) ? (time_t)DBL_MIN : (time_t)FLT_MIN ); + #ifndef WILDABBR /* ** Someone might make incorrect use of a time zone abbreviation: @@ -1683,11 +1708,16 @@ increment_overflow(number, delta) int * number; int delta; { - int number0; + unsigned number0 = (unsigned)*number; + unsigned number1 = (unsigned)(number0 + delta); + + *number = (int)number1; - number0 = *number; - *number += delta; - return (*number < number0) != (delta < 0); + if (delta >= 0) { + return ((int)number1 < (int)number0); + } else { + return ((int)number1 > (int)number0); + } } static int @@ -1695,11 +1725,16 @@ long_increment_overflow(number, delta) long * number; int delta; { - long number0; + unsigned long number0 = (unsigned long)*number; + unsigned long number1 = (unsigned long)(number0 + delta); + + *number = (long)number1; - number0 = *number; - *number += delta; - return (*number < number0) != (delta < 0); + if (delta >= 0) { + return ((long)number1 < (long)number0); + } else { + return ((long)number1 > (long)number0); + } } static int @@ -1868,14 +1903,14 @@ const int do_norm_secs; } else dir = tmcomp(&mytm, &yourtm); if (dir != 0) { if (t == lo) { - ++t; - if (t <= lo) + if (t == TIME_T_MAX) return WRONG; + ++t; ++lo; } else if (t == hi) { - --t; - if (t >= hi) + if (t == TIME_T_MIN) return WRONG; + --t; --hi; } if (lo > hi) right now i'm going to work around this by building the tzcode part of the C library with -fno-strict-overflow (because i don't know how many other places are relying on this unspecified behavior), but i'll apply whatever patch goes into upstream as soon as it's available. --elliott

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[PATCH] * .gitignore: Add 'date'.
by Paul Eggert Aug. 22, 2013

Aug. 22, 2013

--- .gitignore | 1 + 1 file changed, 1 insertion(+) diff --git a/.gitignore b/.gitignore index 5759d2a..18dbbcc 100644 --- a/.gitignore +++ b/.gitignore @@ -4,6 +4,7 @@ *.txt *~ ChangeLog +date leapseconds time.tab tzselect -- 1.7.11.7

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[PATCH] tzselect: new options -c COORD and -n LIMIT
by Paul Eggert Aug. 22, 2013

Aug. 22, 2013

These let the user select TZ based on geographical coordinates. Combining '-c COORD' with '-t time' better insulates the user from issues of nationality. * tzselect.8 (SYNOPSIS, OPTIONS): Document the new options. * tzselect.ksh: Implement them, using the great-circle special case of the Vicenty formula for distances on ellipsoids. (LC_ALL): Set to C, since tzselect is English only. That way, we treat decimal-points in -c option operands the same in all environments. (usage): Document new options. Document existing ones better. (output_distances): New variable. --- tzselect.8 | 26 ++++++++++ tzselect.ksh | 162 +++++++++++++++++++++++++++++++++++++++++++++++++++++++---- 2 files changed, 177 insertions(+), 11 deletions(-) diff --git a/tzselect.8 b/tzselect.8 index b5e2c88..884af36 100644 --- a/tzselect.8 +++ b/tzselect.8 @@ -4,6 +4,12 @@ tzselect \- select a time zone .SH SYNOPSIS .B tzselect [ +.B \-c +.I coord +] [ +.B \-n +.I limit +] [ .B \-t .I zonetabtype ] [ @@ -21,6 +27,26 @@ The output is suitable as a value for the TZ environment variable. All interaction with the user is done via standard input and standard error. .SH OPTIONS .TP +.BI "\-c " coord +Instead of asking for continent and then country and then city, +ask for selection from time zones whose largest cities +are closest to the location with geographical coordinates +.IR coord . +Use ISO 6709 notation for +.IR coord , +for example, +.B "\-c\ \+42.391415\-071.570419" +for 42.391415\(de\|N, 71.570419\(de\|W, and +.B "\-c\ +404226\-0740319" +for 48\(de\|42\(fm\|26\(sd\|N, 74\(de\|3\(fm\|19\(sd\|W. +.TP +.BI "\-n " limit +When +.B \-c +is used, display the closest +.I limit +locations (default 10). +.TP .BI "\-t " zonetabtype Make selections from the time zone table of type .IR zonetabtype . diff --git a/tzselect.ksh b/tzselect.ksh index dc9f256..da6adb2 100644 --- a/tzselect.ksh +++ b/tzselect.ksh @@ -1,5 +1,7 @@ #!/bin/bash +export LC_ALL=C + PKGVERSION='(tzcode) ' TZVERSION=see_Makefile REPORT_BUGS_TO=tz(a)iana.org @@ -41,15 +43,43 @@ ZONETABTYPE=zone exit 1 } -usage="Usage: tzselect [--version] [--help] [-t ZONETABTYPE] +coord= +location_limit=10 + +usage="Usage: tzselect [--version] [--help] [-c COORD] [-n LIMIT] [-t ZONETABTYPE] Select a time zone interactively. -ZONETABTYPE should be one of 'time' or 'zone'. + +Options: + + -c COORD + Instead of asking for continent and then country and then city, + ask for selection from time zones whose largest cities + are closest to the location with geographical coordinates COORD. + COORD should use ISO 6709 notation, for example, '-c +4852+00220' + for Paris. + + -n LIMIT + Display at most LIMIT locations when -c is used (default $location_limit). + + -t ZONETABTYPE + Use time zone table ZONETABTYPE. ZONETABTYPE should be one of + 'time' or 'zone'. + + --version + Output version information. + + --help + Output this help. Report bugs to $REPORT_BUGS_TO." -while getopts t:-: opt +while getopts c:n:t:-: opt do case $opt$OPTARG in + c*) + coord=$OPTARG ;; + n*) + location_limit=$OPTARG ;; t*) ZONETABTYPE=$OPTARG ;; -help) @@ -90,6 +120,66 @@ case $(echo 1 | (select x in x; do break; done) 2>/dev/null) in ?*) PS3= esac +# Awk script to read a time zone table and output the same table, +# with each column preceded by its distance from 'here'. +output_distances=' + BEGIN { + FS = "\t" + while (getline <TZ_COUNTRY_TABLE) + if ($0 ~ /^[^#]/) + country[$1] = $2 + country["US"] = "US" # Otherwise the strings get too long. + } + function cvt1(coord, deg, min, ilen, sign, sec) { + ilen = length(coord) + sign = substr(coord, 1, 1) + if (coord ~ /\./) { + deg = coord + 0 + } else { + if (ilen <= 6) { + sec = 0 + } else { + sec = sign substr(coord, ilen - 1) + ilen -= 2 + } + min = sign substr(coord, ilen - 1, 2) + deg = substr(coord, 1, ilen - 2) + deg = (deg * 3600.0 + min * 60.0 + sec) / 3600.0 + } + return deg * 0.017453292519943295 + } + function convert_latitude(coord) { + match(coord, /..*[-+]/) + return cvt1(substr(coord, 1, RLENGTH - 1)) + } + function convert_longitude(coord) { + match(coord, /..*[-+]/) + return cvt1(substr(coord, RLENGTH)) + } + # Great-circle distance between points with given latitude and longitude. + # Inputs and output are in radians. This uses the great-circle special + # case of the Vicenty formula for distances on ellipsoids. + function dist(lat1, long1, lat2, long2, dlong, x, y, num, denom) { + dlong = long2 - long1 + x = cos (lat2) * sin (dlong) + y = cos (lat1) * sin (lat2) - sin (lat1) * cos (lat2) * cos (dlong) + num = sqrt (x * x + y * y) + denom = sin (lat1) * sin (lat2) + cos (lat1) * cos (lat2) * cos (dlong) + return atan2(num, denom) + } + BEGIN { + coord_lat = convert_latitude(coord) + coord_long = convert_longitude(coord) + } + /^[^#]/ { + here_lat = convert_latitude($2) + here_long = convert_longitude($2) + line = $1 "\t" $2 "\t" $3 "\t" country[$1] + if (NF == 4) + line = line " - " $4 + printf "%g\t%s\n", dist(coord_lat, coord_long, here_lat, here_long), line + } +' # Begin the main loop. We come back here if the user wants to retry. while @@ -101,10 +191,14 @@ while country= region= + case $coord in + ?*) + continent=coord;; + '') # Ask the user for continent or ocean. - echo >&2 'Please select a continent or ocean.' + echo >&2 'Please select a continent, ocean, "coord", or "TZ".' select continent in \ Africa \ @@ -117,7 +211,8 @@ while Europe \ 'Indian Ocean' \ 'Pacific Ocean' \ - 'none - I want to specify the time zone using the Posix TZ format.' + 'coord - I want to use geographical coordinates.' \ + 'TZ - I want to specify the time zone using the Posix TZ format.' do case $continent in '') @@ -130,10 +225,12 @@ while break esac done + esac + case $continent in '') exit 1;; - none) + TZ) # Ask the user for a Posix TZ string. Check that it conforms. while echo >&2 'Please enter the desired value' \ @@ -158,6 +255,45 @@ while done TZ_for_date=$TZ;; *) + case $continent in + coord) + case $coord in + '') + echo >&2 'Please enter coordinates' \ + 'in ISO 6709 notation.' + echo >&2 'For example, +4042-07403 stands for' + echo >&2 '40 degrees 42 minutes north,' \ + '74 degrees 3 minutes west.' + read coord;; + esac + distance_table=$($AWK \ + -v coord="$coord" \ + -v TZ_COUNTRY_TABLE="$TZ_COUNTRY_TABLE" \ + "$output_distances" <$TZ_ZONE_TABLE | + sort -n | + sed "${location_limit}q" + ) + regions=$(echo "$distance_table" | $AWK ' + BEGIN { FS = "\t" } + { print $NF } + ') + echo >&2 'Please select one of the following' \ + 'time zone regions,' + echo >&2 'listed roughly in increasing order' \ + "of distance from $coord". + select region in $regions + do + case $region in + '') echo >&2 'Please enter a number in range.';; + ?*) break;; + esac + done + TZ=$(echo "$distance_table" | $AWK -v region="$region" ' + BEGIN { FS="\t" } + $NF == region { print $4 } + ') + ;; + *) # Get list of names of countries in the continent or ocean. countries=$($AWK -F'\t' \ -v continent="$continent" \ @@ -185,7 +321,8 @@ while # If there's more than one country, ask the user which one. case $countries in *"$newline"*) - echo >&2 'Please select a country.' + echo >&2 'Please select a country' \ + 'whose clocks agree with yours.' select country in $countries do case $country in @@ -256,6 +393,7 @@ while } $1 == cc && $4 == region { print $3 } ' <$TZ_ZONE_TABLE) + esac # Make sure the corresponding zoneinfo file exists. TZ_for_date=$TZDIR/$TZ @@ -292,9 +430,11 @@ Universal Time is now: $UTdate." echo >&2 "" echo >&2 "The following information has been given:" echo >&2 "" - case $country+$region in - ?*+?*) echo >&2 " $country$newline $region";; - ?*+) echo >&2 " $country";; + case $country%$region%$coord in + ?*%?*%) echo >&2 " $country$newline $region";; + ?*%%) echo >&2 " $country";; + %?*%?*) echo >&2 " coord $coord$newline $region";; + %%?*) echo >&2 " coord $coord";; +) echo >&2 " TZ='$TZ'" esac echo >&2 "" @@ -313,7 +453,7 @@ Universal Time is now: $UTdate." '') exit 1;; Yes) break esac -do : +do coord= done case $SHELL in -- 1.8.1.2

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[PATCH 1/3] Further removal of attempt to support floating-point time_t.
by Paul Eggert Aug. 19, 2013

Aug. 19, 2013

* localtime.c (timesub): * zdump.c (my_localtime): Don't worry about time_t being floating-point. * localtime.c (timesub): Avoid undefined behavior on integer overflow when assigning time_t to int. --- localtime.c | 5 +++-- zdump.c | 2 +- 2 files changed, 4 insertions(+), 3 deletions(-) diff --git a/localtime.c b/localtime.c index 5312ad9..f58b20a 100644 --- a/localtime.c +++ b/localtime.c @@ -1489,9 +1489,10 @@ timesub(const time_t *const timep, const int_fast32_t offset, register int leapdays; tdelta = tdays / DAYSPERLYEAR; - idelta = tdelta; - if (tdelta - idelta >= 1 || idelta - tdelta >= 1) + if (! ((! TYPE_SIGNED(time_t) || INT_MIN <= tdelta) + && tdelta <= INT_MAX)) return NULL; + idelta = tdelta; if (idelta == 0) idelta = (tdays < 0) ? -1 : 1; newy = y; diff --git a/zdump.c b/zdump.c index 36c1838..fa5f8d8 100644 --- a/zdump.c +++ b/zdump.c @@ -244,7 +244,7 @@ my_localtime(time_t *tp) tm = *tmp; t = mktime(&tm); - if (t - *tp >= 1 || *tp - t >= 1) { + if (t != *tp) { (void) fflush(stdout); (void) fprintf(stderr, "\n%s: ", progname); (void) fprintf(stderr, tformat(), *tp); -- 1.8.1.2

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Re: [tz] Problem with Busingen
by Paul Eggert Aug. 19, 2013

Aug. 19, 2013

Luca Marzolla wrote: > It is possible to fix this minor inconvenience in the next release? Yes. The problem should already be fixed in the experimental version, which you can get from Github, here: https://github.com/eggert/tz It's fixed in a different way, by the way: the Busingen link got moved to a different file. See: https://github.com/eggert/tz/commit/df99923bde035a263493f3435db63db15df14d53

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Mushroom clowds are forming…
by Steffen Daode Nurpmeso Aug. 17, 2013

Aug. 17, 2013

So if there is a button, someone surely is going to press it. --steffen

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[PATCH] * date.c (nondigit): Add ATTRIBUTE_PURE, to pacify GCC 4.8.1.
by Paul Eggert Aug. 17, 2013

Aug. 17, 2013

--- date.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/date.c b/date.c index 4355a7b..d8ff50e 100644 --- a/date.c +++ b/date.c @@ -497,7 +497,7 @@ errensure(void) retval = EXIT_FAILURE; } -static const char * +static const char * ATTRIBUTE_PURE nondigit(register const char *cp) { while (is_digit(*cp)) -- 1.7.11.7

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