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Improving tzcode localtime.c security a la FreeBSD
by Paul Eggert Sept. 29, 2025

Sept. 29, 2025

The first difference between FreeBSD and tzcode localtime.c that I'd like to address is that FreeBSD is more cautious about handling outlandish TZ settings like "../foo". It seems to me that tzcode should largely mimic FreeBSD's extra caution. In the long run I'd like tzcode localtime.c to be byte-for-byte identical to FreeBSD localtime.c but it's better to do this one step at a time and this security caution is a good first step. I noticed some minor issues with the FreeBSD implementation of this extra checking, so I propose implementing it in a somewhat different way in tzcode. I'm attaching proposed patches to do that, and have installed them in the tzcode development repository on GitHub. Here are issues I noticed: * With an environment variable setting like TZ="/usr/share/zoneinfo/America/Los_Angeles", in a privileged program FreeBSD first opens the directory /usr/share/zoneinfo to get a directory file descriptor, and then uses fstatat and openat, both with AT_RESOLVE_BENEATH. However, it passes the full name to fstatat which must be a typo; I can't see how that would work reliably for a setuid program, even though the neighboring code suggests it was intended to work. I assume it was intended to pass a relative name to fstatat. * As near as I can make out, in privileged programs FreeBSD rejects adjacent slashes in settings like TZ="/usr/share/zoneinfo//America/Los_Angeles", where there are two slashes after "zoneinfo". It would be nicer to treat those two slashes as if they were one, as the kernel does. * tzcode is intended to be portable to platforms lacking openat and AT_RESOLVE_BENEATH, so for now the attached patches mimic FreeBSD's extra checking without using these two features. There are efficiency motivations for using the two features if available, but I'd like to defer that to a later patchset. * Although FreeBSD takes some steps to treat TZ settings the same regardless of whether they come from the TZ environment variable, it doesn't take this idea to its logical conclusion. It seems to me that it's better to not care where the TZ setting came from, as that's easier to document, understand, and maintain, so the attached patches do that. * FreeBSD uses issetugid, which is not universally available. The attached patches work around this by supplying an issetugid substitute for platforms like GNU/Linux that lack it. The first attached patch is a minor indenting fixup. The second one is a minor efficiency improvement, to use strnlen instead of strlen when that improves asymptotic efficiency. The third patch adopts FreeBSD's idea of treating a TZ setting starting with "/usr/share/zoneinfo/" as if it lacked that prefix. And the fourth and main patch changes the tzcode security checks as described above. These tzcode patches do not address other differences between tzcode and FreeBSD, such as the multithreading differences or the check-for-changes differences. These can wait for later patchsets. Comments and suggestions are welcome as usual.

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[PROPOSED] Also treat space as bogus in abbreviations
by Paul Eggert Sept. 29, 2025

Sept. 29, 2025

* NEWS: Mention this. * localtime.c (scrub_abbrs): Treat ' ' as bogus. --- NEWS | 5 +++++ localtime.c | 1 - 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/NEWS b/NEWS index 0436c615..2c354038 100644 --- a/NEWS +++ b/NEWS @@ -51,6 +51,11 @@ Unreleased, experimental changes -DHAVE_GETRESUID=[01], and -DHAVE_GETEUID=[01] to enable or disable these system calls' use. + tzset etc. now treat ' ' like '_' in time zone abbreviations, + just as they treat other invalid bytes. This continues the + transition begun in release 96k, which removed spaces in tzdata + because the spaces break time string parsers. + tzcode now uses mempcpy if available, guessing its availability. Compile with -DHAVE_MEMPCPY=1 or 0 to override the guess. diff --git a/localtime.c b/localtime.c index c5bc4e93..aa9ad7bd 100644 --- a/localtime.c +++ b/localtime.c @@ -504,7 +504,6 @@ scrub_abbrs(struct state *sp) for (i = 0; i < sp->charcnt; ++i) switch (sp->chars[i]) { case '\0': - case ' ': case '+': case '-': case '.': case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9': -- 2.48.1

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[PATCH 1/3] Prefer mempcpy to doing it by hand
by Paul Eggert Sept. 29, 2025

Sept. 29, 2025

This is less error-prone. Supply a mempcpy if the system lacks it. * Makefile, NEWS: Mention this. * localtime.c (tzloadbody, tzparse): * zic.c (random_dirent, relname, doabbr): * zdump.c (my_snprintf) [!HAVE_SNPRINTF]: (istrftime): Prefer mempcpy to doing it by hand. * private.h (HAVE_MEMPCPY): New macro. (mempcpy) [!HAVE_MEMPCPY]: New function. --- Makefile | 1 + NEWS | 3 +++ localtime.c | 13 +++++++------ private.h | 17 +++++++++++++++++ zdump.c | 11 +++++++---- zic.c | 36 ++++++++++++++++++++---------------- 6 files changed, 55 insertions(+), 26 deletions(-) diff --git a/Makefile b/Makefile index 83122ecc..5b577781 100644 --- a/Makefile +++ b/Makefile @@ -262,6 +262,7 @@ LDLIBS= # -DHAVE_LOCALTIME_RZ=0 if you do not want zdump to use localtime_rz # localtime_rz can make zdump significantly faster, but is nonstandard. # -DHAVE_MALLOC_ERRNO=0 if malloc etc. do not set errno on failure. +# -DHAVE_MEMPCPY=1 if your system has mempcpy, 0 if not (default is guessed) # -DHAVE_POSIX_DECLS=0 if your system's include files do not declare # functions like 'link' or variables like 'tzname' required by POSIX # -DHAVE_SETENV=0 if your system lacks the setenv function diff --git a/NEWS b/NEWS index 5c4786cb..0436c615 100644 --- a/NEWS +++ b/NEWS @@ -51,6 +51,9 @@ Unreleased, experimental changes -DHAVE_GETRESUID=[01], and -DHAVE_GETEUID=[01] to enable or disable these system calls' use. + tzcode now uses mempcpy if available, guessing its availability. + Compile with -DHAVE_MEMPCPY=1 or 0 to override the guess. + tzcode now uses strnlen to improve asymptotic performance a bit. Compile with -DHAVE_STRNLEN=0 if your platform lacks it. diff --git a/localtime.c b/localtime.c index 67500312..316c7504 100644 --- a/localtime.c +++ b/localtime.c @@ -624,6 +624,7 @@ tzloadbody(char const *name, struct state *sp, char tzloadflags, } if (!SUPPRESS_TZDIR && name[0] != '/') { + char *cp; if (sizeof lsp->fullname - sizeof tzdirslash <= strnlen(name, sizeof lsp->fullname - sizeof tzdirslash)) return ENAMETOOLONG; @@ -631,8 +632,9 @@ tzloadbody(char const *name, struct state *sp, char tzloadflags, /* Create a string "TZDIR/NAME". Using sprintf here would pull in stdio (and would fail if the resulting string length exceeded INT_MAX!). */ - memcpy(lsp->fullname, tzdirslash, sizeof tzdirslash); - strcpy(lsp->fullname + sizeof tzdirslash, name); + cp = lsp->fullname; + cp = mempcpy(cp, tzdirslash, sizeof tzdirslash); + strcpy(cp, name); name = lsp->fullname; } @@ -1471,12 +1473,11 @@ tzparse(const char *name, struct state *sp, struct state const *basep) } sp->charcnt = charcnt; cp = sp->chars; - memcpy(cp, stdname, stdlen); - cp += stdlen; + cp = mempcpy(cp, stdname, stdlen); *cp++ = '\0'; if (dstlen != 0) { - memcpy(cp, dstname, dstlen); - *(cp + dstlen) = '\0'; + cp = mempcpy(cp, dstname, dstlen); + *cp = '\0'; } return true; } diff --git a/private.h b/private.h index 6ae0c2fd..867340fa 100644 --- a/private.h +++ b/private.h @@ -837,6 +837,23 @@ extern char *asctime_r(struct tm const *restrict, char *restrict); extern char **environ; #endif +#ifndef HAVE_MEMPCPY +# if (defined mempcpy \ + || defined __FreeBSD__ || defined __NetBSD__ || defined __linux__) +# define HAVE_MEMPCPY 1 +# else +# define HAVE_MEMPCPY 0 +# endif +#endif +#if !HAVE_MEMPCPY +static void * +mempcpy(char *restrict s1, char const *restrict s2, size_t n) +{ + char *p = memcpy(s1, s2, n); + return p + n; +} +#endif + #if 2 <= HAVE_TZNAME + (TZ_TIME_T || !HAVE_POSIX_DECLS) extern char *tzname[]; #endif diff --git a/zdump.c b/zdump.c index 8e836e60..93fe05cb 100644 --- a/zdump.c +++ b/zdump.c @@ -927,6 +927,7 @@ my_snprintf(char *s, size_t size, char const *format, ...) int n; va_list args; char const *arg; + char *cp; size_t arglen, slen; char buf[1024]; va_start(args, format); @@ -943,8 +944,9 @@ my_snprintf(char *s, size_t size, char const *format, ...) arglen = n; } slen = arglen < size ? arglen : size - 1; - memcpy(s, arg, slen); - s[slen] = '\0'; + cp = s; + cp = mempcpy(cp, arg, slen); + *cp = '\0'; n = arglen <= INT_MAX ? arglen : -1; va_end(args); return n; @@ -1073,8 +1075,9 @@ istrftime(char *buf, ptrdiff_t size, char const *time_fmt, char fbuf[100]; bool oversized = sizeof fbuf <= f_prefix_copy_size; char *f_prefix_copy = oversized ? xmalloc(f_prefix_copy_size) : fbuf; - memcpy(f_prefix_copy, f, f_prefix_len); - strcpy(f_prefix_copy + f_prefix_len, "X"); + char *cp = f_prefix_copy; + cp = mempcpy(cp, f, f_prefix_len); + strcpy(cp, "X"); formatted_len = strftime(b, s, f_prefix_copy, tm); if (oversized) free(f_prefix_copy); diff --git a/zic.c b/zic.c index 6bdb039d..e78dfd47 100644 --- a/zic.c +++ b/zic.c @@ -1327,10 +1327,10 @@ random_dirent(char const **name, char **namealloc) uint_fast64_t unfair_min = - ((UINTMAX_MAX % base__6 + 1) % base__6); if (!dst) { - dst = xmalloc(size_sum(dirlen, prefixlen + suffixlen + 1)); - memcpy(dst, src, dirlen); - memcpy(dst + dirlen, prefix, prefixlen); - dst[dirlen + prefixlen + suffixlen] = '\0'; + char *cp = dst = xmalloc(size_sum(dirlen, prefixlen + suffixlen + 1)); + cp = mempcpy(cp, src, dirlen); + cp = mempcpy(cp, prefix, prefixlen); + cp[suffixlen] = '\0'; *name = *namealloc = dst; } @@ -1430,15 +1430,17 @@ relname(char const *target, char const *linkname) if (*linkname == '/') { /* Make F absolute too. */ size_t len = strlen(directory); - size_t lenslash = len + (len && directory[len - 1] != '/'); + bool needs_slash = len && directory[len - 1] != '/'; + size_t lenslash = len + needs_slash; size_t targetsize = strlen(target) + 1; + char *cp; if (*directory != '/') return NULL; linksize = size_sum(lenslash, targetsize); - f = result = xmalloc(linksize); - memcpy(result, directory, len); - result[len] = '/'; - memcpy(result + lenslash, target, targetsize); + f = cp = result = xmalloc(linksize); + cp = mempcpy(cp, directory, len); + *cp = '/'; + memcpy(cp + needs_slash, target, targetsize); } for (i = 0; f[i] && f[i] == linkname[i]; i++) if (f[i] == '/') @@ -1448,11 +1450,13 @@ relname(char const *target, char const *linkname) taillen = strlen(f + dir_len); dotdotetcsize = size_sum(size_product(dotdots, 3), taillen + 1); if (dotdotetcsize <= linksize) { + char *cp; if (!result) result = xmalloc(dotdotetcsize); + cp = result; for (i = 0; i < dotdots; i++) - memcpy(result + 3 * i, "../", 3); - memmove(result + 3 * dotdots, f + dir_len, taillen + 1); + cp = mempcpy(cp, "../", 3); + memmove(cp, f + dir_len, taillen + 1); } return result; } @@ -2875,11 +2879,11 @@ doabbr(char *abbr, struct zone const *zp, char const *letters, else if (letters == disable_percent_s) return 0; sprintf(abbr, format, letters); - } else if (isdst) { - strcpy(abbr, slashp + 1); - } else { - memcpy(abbr, format, slashp - format); - abbr[slashp - format] = '\0'; + } else if (isdst) + strcpy(abbr, slashp + 1); + else { + char *abbrend = mempcpy(abbr, format, slashp - format); + *abbrend = '\0'; } len = strlen(abbr); if (!doquotes) -- 2.48.1

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Changes to moderation procedures
by James Mitchell Sept. 29, 2025

Sept. 29, 2025

Hi all, We've made a small update to moderation settings in response to recent spam: * First posts from new members will be held for review. Once approved, the moderation flag will be removed. * All posts from non-members will continue to be held for moderation. A few existing members currently have moderation enabled. You may experience brief delays while these changes take effect—thank you for your patience. If you believe your messages are being held in error, please contact the list owners at tz-owner(a)iana.org<mailto:tz-owner@iana.org>. Kind regards, James Mitchell IANA

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List moderation
by Kim Davies Sept. 24, 2025

Sept. 24, 2025

Hi folks, Our team have removed the list subscriber that flooded the list with emails in the last few minutes, and have put some emergency moderation in place until we can confirm it has died down. Apologies for the noise. kim

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Prevent spam
by stan＠ulbrych.org Sept. 24, 2025

Sept. 24, 2025

Hello, I just received a barrage of emails (over 50) due to spam messages, I suggest the list owners look into first posts requiring approval before they are published. This is done for example in the Python docs list, and allows for such spam to be prevented. Best Regards, Stan Ulbrych

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List moderation
by Kim Davies Sept. 24, 2025

Sept. 24, 2025

Hi folks, Our team have removed the list subscriber that flooded the list with emails in the last few minutes, and have put some emergency moderation in place until we can confirm it has died down. Apologies for the noise. kim

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CRA auditor in BC checked commute route and distance in Toronto at rush hour BC time
by Brian Inglis Sept. 7, 2025

Sept. 7, 2025

How Google Maps helped one Toronto commuter beat traffic - and the tax collector: https://www.cbc.ca/news/canada/british-columbia/traffic-relocation-tax-cour… CRA auditor in BC checked commute route distance in Toronto at rush hour BC time! -- Take care. Thanks, Brian Inglis Calgary, Alberta, Canada La perfection est atteinte Perfection is achieved non pas lorsqu'il n'y a plus rien à ajouter not when there is no more to add mais lorsqu'il n'y a plus rien à retrancher but when there is no more to cut -- Antoine de Saint-Exupéry

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TZLOAD_FROMENV flag used incorrectly
by Dag-Erling Smørgrav Aug. 31, 2025

Aug. 31, 2025

tzset_unlocked() calls zoneinit() with TZLOAD_STRINGS | TZLOAD_FROMENV regardless of whether name actually came from the environment. If name is null, zoneinit() will use TZDEFAULT instead, but will incorrectly consider that to be tainted, and unnecessarily perform an access check before trying to open it. That is luckily harmless in unmodified tzcode, but I would still prefer if TZLOAD_FROMENV were only set when actually true; see attached patch. DES -- Dag-Erling Smørgrav - des(a)des.no

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[PROPOSED] Update tz-link for FTP, Go, Levine proposal
by Paul Eggert Aug. 31, 2025

Aug. 31, 2025

* tz-link.html: Remove links to projects that seem to be dead: MINIX, tziCal, tzdist-bis, Australian Parliamentary Library pub. Remove ftp: links as modern browsers don’t support them; instead, just mention FTP (and rsync, while we’re at it). Go seems to have fixed its 32-bit time_t bug. Cite British Sleep Society position paper on DST, and move the medical citations to a new list. Update citation to Judah Levine’s proposal to use 13-second leap smears every decade, as a substitute for leap seconds. --- tz-link.html | 115 +++++++++++++++++++++++++++------------------------ 1 file changed, 60 insertions(+), 55 deletions(-) diff --git a/tz-link.html b/tz-link.html index 76566224..669a3cb8 100644 --- a/tz-link.html +++ b/tz-link.html @@ -84,7 +84,6 @@ title="Berkeley Software Distribution">BSD</abbr></a>, <a href="https://www.chromium.org/chromium-os/">ChromiumOS</a>, <a href="https://cygwin.com">Cygwin</a>, <a href="https://mariadb.org">MariaDB</a>, -<a href="https://en.wikipedia.org/wiki/MINIX">MINIX</a>, <a href="https://musl.libc.org">musl libc</a>, <a href="https://www.mysql.com">MySQL</a>, <a href="https://en.wikipedia.org/wiki/WebOS"><abbr @@ -175,12 +174,15 @@ ustar interchange format</a>, compressed as described above; older releases use a nearly compatible format. Since version 2016h, each release has contained a text file named “<code>version</code>” whose first (and currently only) line is the version. -Older releases are <a href="https://ftp.iana.org/tz/releases/">archived</a>, -and are also available in an -<a href="ftp://ftp.iana.org/tz/releases/"><abbr -title="File Transfer Protocol">FTP</abbr> directory</a> via a -less secure protocol.</p> -<p>Alternatively, a development repository of code and data can be +<a href="https://ftp.iana.org/tz/releases/">Older archived releases are +available</a> via +<a href="https://en.wikipedia.org/wiki/HTTPS"><abbr +title="Hypertext Transfer Protocol Secure">HTTPS</abbr></a>, +<a href="https://en.wikipedia.org/wiki/Rsync"><abbr +title="remote sync">rsync</abbr></a>, and +<a href="https://en.wikipedia.org/wiki/FTP"><abbr +title="File Transfer Protocol">FTP</abbr></a>. +<p>Alternatively, a development repository of code and data can bem retrieved from <a href="https://github.com">GitHub</a> via the shell command:</p> <pre><code><a href="https://git-scm.com">git</a> clone <a href="https://github.com/eggert/tz">https://github.com/eggert/tz</a> @@ -195,7 +197,7 @@ After obtaining the code and data files, see the The code lets you compile the <code><abbr>tz</abbr></code> source files into machine-readable binary files, one for each location. The binary files are in a special format specified by -<a href="https://www.rfc-editor.org/rfc/9636">The +<a href="https://www.rfc-editor.org/rfc/rfc9636">The Time Zone Information Format (<abbr>TZif</abbr>)</a> (Internet <abbr title="Request For Comments">RFC</abbr> 9636). The code also lets @@ -249,7 +251,7 @@ with lines terminated by <a href="https://en.wikipedia.org/wiki/Newline"><abbr title="linefeed">LF</abbr></a>, which can be modified by common text editors such as <a href="https://www.gnu.org/software/emacs/">GNU Emacs</a>, -<a href="https://gedit-technology.github.io/apps/gedit/">gedit</a>, and +<a href="https://gedit-text-editor.org">gedit</a>, and <a href="https://www.vim.org">vim</a>. Specialized source-file editing can be done via the <a href="https://packagecontrol.io/packages/zoneinfo">Sublime @@ -377,21 +379,16 @@ calculates the current time difference between locations.</li> <section> <h2 id="protocols">Network protocols for <code><abbr>tz</abbr></code> data</h2> <ul> -<li>The <a href="https://www.ietf.org">Internet Engineering Task Force</a>’s -<a href="https://datatracker.ietf.org/wg/tzdist/charter/">Time Zone Data -Distribution Service (tzdist) working group</a> defined <a -href="https://www.rfc-editor.org/rfc/rfc7808">TZDIST</a> -(Internet <abbr>RFC</abbr> 7808), a time zone data distribution service, -along with <a href="https://www.rfc-editor.org/rfc/rfc7809">CalDAV</a> +<li><a href="https://www.rfc-editor.org/rfc/rfc7808">Time Zone +Data Distribution Service</a> (TZDIST, Internet <abbr>RFC</abbr> 7808) +is associated with +<a href="https://www.rfc-editor.org/rfc/rfc7809">CalDAV</a> (Internet <abbr>RFC</abbr> 7809), a calendar access protocol for transferring time zone data by reference. <a href="https://devguide.calconnect.org/Time-Zones/TZDS/">TZDIST -implementations</a> are available. -The <a href="https://www.ietf.org/mailman/listinfo/tzdist-bis">tzdist-bis -mailing list</a> discusses possible extensions.</li> -<li>The <a href="https://www.rfc-editor.org/rfc/rfc5545"> -Internet Calendaring and Scheduling Core Object Specification -(iCalendar)</a> (Internet <abbr>RFC</abbr> 5445) +implementations</a> are available.</li> +<li>The <a href="https://www.rfc-editor.org/rfc/rfc5545">iCalendar format</a> +(Internet <abbr>RFC</abbr> 5445) covers time zone data; see its VTIMEZONE calendar component. The iCalendar format requires specialized parsers and generators; a @@ -423,10 +420,6 @@ available under the <a href="https://www.gnu.org/copyleft/gpl.html"><abbr>GNU</abbr> General Public License (<abbr title="General Public License">GPL</abbr>)</a>.</li> -<li><a href="https://sourceforge.net/projects/tzical/">tziCal – tz -database conversion utility</a> is like Vzic, except for the <a -href="https://dotnet.microsoft.com">.NET framework</a> -and with a <abbr>BSD</abbr>-style license.</li> <li><a href="https://metacpan.org/release/DateTime-TimeZone">DateTime::TimeZone</a> contains a script <code>parse_olson</code> that compiles @@ -616,6 +609,9 @@ the Apache License.</li> library that translates between <abbr>UT</abbr> and civil time and can read <abbr>TZif</abbr> files. It is freely available under the Apache License.</li> +<li>The <a href="https://golang.org">Go programming language</a> +has a <abbr>TZif</abbr> file reader <a +href="https://pkg.go.dev/time#LoadLocationFromTZData"><code>LoadLocationFromTZData</code></a>.</li> <li>The <a href="https://github.com/nayarsystems/posix_tz_db"><code>posix_tz_db</code> package</a> contains Python code @@ -678,10 +674,6 @@ href="https://www.mozilla.org/en-US/thunderbird/">Thunderbird</a>. It displays multiple clocks in the application window, and has a mapping interface to <a href="https://www.google.com/earth/">Google Earth</a>. It is freely available under the <abbr>GPL</abbr>.</li> -<li><a href="https://golang.org">Go programming language</a> -implementations contain a copy of a 32-bit subset of a recent -<code><abbr>tz</abbr></code> database in a -Go-specific format.</li> <li>Microsoft Windows 8.1 and later has <code><abbr>tz</abbr></code> data and <abbr>CLDR</abbr> data (mentioned <a href="#CLDR">below</a>) used by the @@ -836,7 +828,8 @@ Saving Time – History, rationale, laws & dates</a> and summarized in History of Daylight Saving Time</a>.</li> <li><a href="https://www.laphamsquarterly.org/roundtable/time-lords">Time Lords</a> discusses how authoritarians manipulate civil time.</li> -<li><a href="https://www.w3.org/TR/timezone/">Working with Time Zones</a> +<li><a href="https://www.w3.org/TR/timezone/">Working with Time +and Time Zones</a> contains guidelines and best practices for software applications that deal with civil time.</li> <li><a href="https://webspace.science.uu.nl/~gent0113/idl/idl.htm">A History of @@ -851,10 +844,7 @@ Zone Concepts</a> discusses terminological issues behind time zones.</li> <h2 id="national">National histories of legal time</h2> <dl> <dt>Australia</dt> -<dd>The Parliamentary Library commissioned a <a -href="https://parlinfo.aph.gov.au/parlInfo/download/library/prspub/359V6/upload_b…">research -paper on daylight saving time in Australia</a>. -The Bureau of Meteorology publishes a list of <a +<dd>The Bureau of Meteorology publishes a list of <a href="http://www.bom.gov.au/climate/averages/tables/dst_times.shtml">Implementation Dates of Daylight Savings Time within Australia</a>.</dd> <dt>Belgium</dt> @@ -915,8 +905,8 @@ covers the history of local time in the Netherlands from ancient times.</dd> href="https://www.dia.govt.nz/Daylight-Saving-History">History of Daylight Saving</a>.</dd> <dt>Palestine</dt> -<dd>The Ministry of Telecom and IT publishes a <a -href="https://mtit.pna.ps/home/TimeZone" +<dd>The Ministry of Telecom and Digital Economy publishes a <a +href="https://mtde.gov.ps/home/TimeZone" hreflang="ar">history of clock changes (in Arabic)</a>.</dd> <dt>Portugal</dt> <dd>The Lisbon Astronomical Observatory publishes a @@ -957,9 +947,6 @@ zone shifts, and many scientific studies have been conducted. This section summarizes reviews and position statements based on scientific literature in the area.</p> <ul> -<li>In 2022 the American Medical Association issued a -<a href="https://www.ama-assn.org/press-center/press-releases/ama-calls-permanent-st…">statement -supporting permanent standard time</a> on health grounds.</li> <li>Carey RN, Sarma KM. <a href="https://bmjopen.bmj.com/content/7/6/e014319.long">Impact of daylight saving time on road traffic collision risk: a systematic @@ -969,22 +956,12 @@ This reviews research literature and concludes that the evidence neither supports nor refutes road safety benefits from shifts in time zones.</li> <li>Havranek T, Herman D, Irsova D. -<a href="https://www.iaee.org/en/publications/ejarticle.aspx?id=3051">Does -daylight saving save electricity? A meta-analysis</a>. +Does daylight saving save electricity? A meta-analysis. <em>Energy J.</em> 2018;39(2):35–61. doi:<a href="https://doi.org/10.5547/01956574.39.2.thav">10.5547/01956574.39.2.thav</a>. This analyzes research literature and concludes, “Electricity savings are larger for countries farther away from the equator, while subtropical regions consume more electricity because of <abbr>DST</abbr>.”</li> -<li>Malow BA. <a -href="https://academic.oup.com/sleep/article/45/12/zsac236/6717940">It is time -to abolish the clock change and adopt permanent -standard time in the United States: -a Sleep Research Society position statement</a>. -<em>Sleep.</em> 2022;45(12):zsac236. -doi:<a href="https://doi.org/10.1093/sleep/zsac236">10.1093/sleep/zsac236</a>. -After reviewing the scientific literature, the Sleep Research Society -advocates permanent standard time due to its health benefits. <li>Neumann P, von Blanckenburg K. <a href="https://journals.sagepub.com/doi/full/10.1177/0961463X241310562">What time will it be? A comprehensive literature review on daylight saving time</a>. @@ -993,6 +970,30 @@ doi:<a href="https://doi.org/10.1177/0961463X241310562">10.1177/0961463X24131056 This reviews DST’s effects on electricity, health, crime, road safety, and the economy, focusing on research since 2010, and concludes that year-round standard time is preferable overall. +</ul> + +<p>The following medical societies have taken positions on the +advisability of clock shifts:</p> + +<ul> +<li>In 2022 the American Medical Association issued a +<a href="https://www.ama-assn.org/press-center/press-releases/ama-calls-permanent-st…">statement +supporting permanent standard time</a> on health grounds.</li> +<li>Crawford MR, Winnebeck EC, von Schantz M <em>et al</em>. +<a href="https://onlinelibrary.wiley.com/doi/10.1111/jsr.14352">The +British Sleep Society position statement on Daylight Saving Time in the UK</a>. +<em>J Sleep Res.</em> 2025;34(3):e14352. +doi:<a href="https://doi.org/10.1111/jsr.14352">10.1111/jsr.14352</a>. +This recommends that the UK abolish DST for health reasons.</li> +<li>Malow BA. <a +href="https://academic.oup.com/sleep/article/45/12/zsac236/6717940">It is time +to abolish the clock change and adopt permanent +standard time in the United States: +a Sleep Research Society position statement</a>. +<em>Sleep.</em> 2022;45(12):zsac236. +doi:<a href="https://doi.org/10.1093/sleep/zsac236">10.1093/sleep/zsac236</a>. +After reviewing the scientific literature, the Sleep Research Society +advocates permanent standard time due to its health benefits.</li> <li>Rishi MA, Cheng JY, Strang AR <em>et al</em>. <a href="https://jcsm.aasm.org/doi/10.5664/jcsm.10898">Permanent standard time is the optimal choice for health and safety: @@ -1144,12 +1145,16 @@ to discontinue the use of leap seconds by 2035, and requested that no discontinuous adjustments be made to UTC for at least a century. The World Radiocommunication Conference <a href="https://www.itu.int/dms_pub/itu-r/opb/act/R-ACT-WRC.15-2023-PDF-E.pdf">resolved -in 2023</a> to cooperate with this process. -<a href="https://www.preprints.org/manuscript/202406.0043/v1">A proposal -to change the leap-second adjustments to Coordinated Universal Time</a> -(doi:<a href="https://doi.org/10.1088/1681-7575/ad6266">10.1088/1681-7575/ad6266</a>) -would replace leap seconds with 13-second leap smears occurring once per +in 2023</a> to cooperate with this process. One proposal to implement this +would replace leap seconds with seven 13-second leap smears occurring once per decade until 2100, with leap smears after that gradually increasing in size. +See: +<ul> +<li>Levine J. <a href="https://www.preprints.org/manuscript/202406.0043/v1">A +proposal to change the leap-second adjustments to +coordinated universal time</a>. <em>Metrologia.</em> 2024;61(5):055002. doi:<a +href="https://doi.org/10.1088/1681-7575/ad6266">10.1088/1681-7575/ad6266</a>.</li> +</ul> However, there is still no consensus on whether this is the best way to replace leap seconds. </li> -- 2.48.1

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