December 2025 - tz - lists.iana.org

Whither /usr/share/zoneinfo/right?
by Paul Gilmartin Jan. 8, 2026

Jan. 8, 2026

ISTR on Linux long ago, a subdirectory, /usr/share/zoneinfo/right, which used arguments not POSIX time but TAI. Was that a local hack, or was it removed, possibly because of uncertainty of future leap seconds? -- Thanks, gil

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tzcode and tzdata tar base make checks fail
by Brian Inglis Dec. 31, 2025

Dec. 31, 2025

Cygwin uses separate packages of tzcode programs and tzdata files verbatim to support standard local time zones in preference to limited native data. Running make check on the separate tar file fails in both cases. When I took over the packages, I provided basic checks, but reviewed and changed the builds this release, and would like to reenable the built in checks you provide and mentioned recently. The attached logs show the results of having the package build scripts run `make check` from the package build directory which is set up with symlinks to each of the tar sources. Is there anything obviously missing or incorrect with `make check` invocations which could cause the observed failures, or things that may need changed? -- 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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Time zones on Antarctica expedition
by Brooks Harris Dec. 30, 2025

Dec. 30, 2025

Those who have a New York Times subscription may find this entertaining: Does Anybody Really Know What Time It Is? The clocks aboard our icebreaker will be changed several times en route to Antarctica. It’s one of many things that make the expedition feel otherworldly. https://www.nytimes.com/2025/12/29/climate/antarctica-time-zone.html

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[PROPOSED] Fix some unsequenced/reproducible commentary
by Paul Eggert Dec. 20, 2025

Dec. 20, 2025

* private.h (ATTRIBUTE_CONST, ATTRIBUTE_PURE): In commentary do not say that __attribute__((const)) is stricter than [[unsequenced]], as Jens Gustedt, an originator of [[unsequenced]], wrote in <https://lists.gnu.org/r/bug-gnulib/2025-01/msg00190.html> that some const functions are not unsequenced. To be safe, make a similar change for __attribute__((pure)) and [[reproducible]], though I don’t have confirmation from Jens. --- private.h | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/private.h b/private.h index 074da284..50d6a52a 100644 --- a/private.h +++ b/private.h @@ -619,11 +619,11 @@ typedef unsigned long uintmax_t; # define ATTRIBUTE_UNSEQUENCED /* empty */ #endif -/* GCC attributes that are useful in tzcode. - __attribute__((const)) is stricter than [[unsequenced]], - so the latter is an adequate substitute in non-GCC C23 platforms. - __attribute__((pure)) is stricter than [[reproducible]], - so the latter is an adequate substitute in non-GCC C23 platforms. */ +/* GNU C attributes that are useful in tzcode. + Although neither __attribute__((const)) nor __attribute__((pure)) are + stricter than their C23 counterparts [[unsequenced]] and [[reproducible]], + the C23 attributes happen to work in each tzcode use of ATTRIBUTE_CONST + and ATTRIBUTE_PURE. (This might not work outside of tzcode!) */ #if __GNUC__ < 3 # define ATTRIBUTE_CONST ATTRIBUTE_UNSEQUENCED # define ATTRIBUTE_FORMAT(spec) /* empty */ -- 2.51.0

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TYPE_SIGNED(t) warnings..
by Christos Zoulas Dec. 19, 2025

Dec. 19, 2025

Hi, Gcc with -Wall -Wextra -Wtype-limits produces warnings with: #define TYPE_SIGNED(T) ((T)-1) < 0) error: comparison of unsigned expression in '< 0' is always false [-Werror=type-limits] Perhaps use something that checks the sign bit directly? #define TYPE_SIGNED(T) \ (((T)~(T)0 >> (sizeof(T) * CHAR_BIT - 1)) == (T)-1) Or something from NetBSD's <sys/cdefs.h>? christos

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2025c zic.c calls fflush(3) on read only file pointer.
by Christos Zoulas Dec. 18, 2025

Dec. 18, 2025

Hello, This is undefined behavior. NetBSD returns EOF and sets errno to EBADFD. I am not sure why fflush(3) is called explicitly now, since fclose(3) does it anyway. Best, christos

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[Feature Request] Add validation in zic for invalid DST intervals
by 任春辉 Dec. 16, 2025

Dec. 16, 2025

Hello tzdata maintainers, I would like to propose a feature enhancement for the zic compiler. Currently, the NOS time zone rules are defined as: Rule NOS 1970 2037 - Jan 27 23:43:01 2:0 SDST Rule NOS 1970 2037 - Jan 28 0:51:01 0 S Zone OS/NOS +7:0:0 NOS NO%s Issue: - The first rule enters DST at 23:43:01 with a +2 hour offset, moving local time to 01:43:01. - The second rule is intended to revert to standard time at 00:51:01. - Due to the offset, 00:51:01 local time never occurs, so the second rule will never trigger. - This creates unreachable local times and may cause incorrect results in time calculations. Proposal: - Add validation in the zic command to detect DST rules where the offset causes the subsequent rule's local time to be unreachable. - The validation could issue a warning or error to alert the author of potentially invalid rules. - This would improve the robustness of time zone definitions and prevent subtle bugs in downstream applications. Thank you for your consideration. Best regards

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[PROPOSED] Make HTML view better on cell phones
by Paul Eggert Dec. 15, 2025

Dec. 15, 2025

Unfortunately without the meta viewport element described below, most mobile browers default to unreadably tiny text for backward compatibility with how the iPhone misbehaved in 2007. While we’re giving up on vanilla style, improve readability in minor ways for bigger screens too. Here are the changes made: * Add to HTML files the element <meta name="viewport" content="width=device-width, initial-scale=1">. This is the most common setting mentioned in <https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Elements/meta/n…>. * Style pre elements with "overflow: auto", not "white-space: prewrap". * Decrease pre elements’ margins from 2em to 1.3rem, and change margins/padding for dd and ul to 1.3rem. * In tz-how-to.html, stop trying to package a wideish pre element inside a table, as that’s too painful to do portably and nicely on both narrow and wide screens. Just do a pre followed by a table. --- theory.html | 5 +++- tz-art.html | 4 +++ tz-how-to.html | 72 +++++++++----------------------------------------- tz-link.html | 5 +++- 4 files changed, 25 insertions(+), 61 deletions(-) diff --git a/theory.html b/theory.html index e6e64177..8c802858 100644 --- a/theory.html +++ b/theory.html @@ -3,8 +3,11 @@ <head> <title>Theory and pragmatics of the tz code and data</title> <meta charset="UTF-8"> + <meta name="viewport" content="width=device-width, initial-scale=1"> <style> - pre {margin-left: 2em; white-space: pre-wrap;} + dd {margin-left: 1.3rem;} + pre {margin-left: 1.3rem; overflow: auto;} + ul {padding-left: 1.3rem;} </style> </head> diff --git a/tz-art.html b/tz-art.html index 3039a86f..5f92fa1b 100644 --- a/tz-art.html +++ b/tz-art.html @@ -2,6 +2,10 @@ <html lang="en"> <head> <meta charset="UTF-8"> +<meta name="viewport" content="width=device-width, initial-scale=1"> +<style> +ul {padding-left: 1.3rem;} +</style> <title>Time and the Arts</title> </head> <body> diff --git a/tz-how-to.html b/tz-how-to.html index ccfdc9eb..ddafb2aa 100644 --- a/tz-how-to.html +++ b/tz-how-to.html @@ -3,14 +3,15 @@ <head> <title>How to Read the tz Database</title> <meta charset="UTF-8"> +<meta name="viewport" content="width=device-width, initial-scale=1"> <style> -pre {margin-left: 2em; white-space: pre-wrap;} -pre.td {margin-left: 0;} +pre {margin-left: 1.3rem; overflow: auto;} td {text-align: center;} table {border: 1px outset;} th, td {border: 1px inset;} table.rule {border: none; margin: auto;} td.footnote {text-align: left;} +ul {padding-left: 1.3rem;} </style> </head> <body> @@ -38,16 +39,7 @@ about the zones.</p> for Chicago (from the <code>northamerica</code> file in the <code>data</code> subdirectory):</p> -<table> -<tr> - <th colspan="6">From the Source File</th> -</tr> -<tr> - <td colspan="6"> - <table class="rule"> - <tr><td style="border:none;text-align:left"> -<pre class="td"> -#Rule NAME FROM TO - IN ON AT SAVE LETTER +<pre>#Rule NAME FROM TO - IN ON AT SAVE LETTER Rule Chicago 1920 only - Jun 13 2:00 1:00 D Rule Chicago 1920 1921 - Oct lastSun 2:00 0 S Rule Chicago 1921 only - Mar lastSun 2:00 1:00 D @@ -55,8 +47,7 @@ Rule Chicago 1922 1966 - Apr lastSun 2:00 1:00 D Rule Chicago 1922 1954 - Sep lastSun 2:00 0 S Rule Chicago 1955 1966 - Oct lastSun 2:00 0 S </pre> - </td></tr></table></td> -</tr> +<table> <tr> <th colspan="6">Reformatted a Bit</th> </tr> @@ -160,16 +151,7 @@ time changed in 1955. Got it?</p> <p>OK, now for the somewhat more interesting “US” rules:</p> -<table> -<tr> - <th colspan="6">From the Source File</th> -</tr> -<tr> - <td colspan="6"> - <table class="rule"> - <tr><td style="border:none;text-align:left"> -<pre class="td"> -#Rule NAME FROM TO - IN ON AT SAVE LETTER/S +<pre>#Rule NAME FROM TO - IN ON AT SAVE LETTER/S Rule US 1918 1919 - Mar lastSun 2:00 1:00 D Rule US 1918 1919 - Oct lastSun 2:00 0 S Rule US 1942 only - Feb 9 2:00 1:00 W # War @@ -184,8 +166,7 @@ Rule US 1987 2006 - Apr Sun>=1 2:00 1:00 D Rule US 2007 max - Mar Sun>=8 2:00 1:00 D Rule US 2007 max - Nov Sun>=1 2:00 0 S </pre> - </td></tr></table></td> -</tr> +<table> <tr> <th colspan="6">Reformatted a Bit</th> </tr> @@ -328,15 +309,7 @@ rule, so there should be no change.</li> <p>OK, now let’s look at a Zone record:</p> -<table> -<tr> - <th colspan="5">From the Source File</th> -</tr> -<tr> - <td colspan="5"> - <table class="rule"> - <tr><td style="border:none;text-align:left"> -<pre class="td"> +<pre> #Zone NAME STDOFF RULES FORMAT [UNTIL] Zone America/Chicago -5:50:36 - LMT 1883 Nov 18 12:09:24 -6:00 US C%sT 1920 @@ -347,8 +320,7 @@ Zone America/Chicago -5:50:36 - LMT 1883 Nov 18 12:09:24 -6:00 Chicago C%sT 1967 -6:00 US C%sT </pre> - </td></tr></table></td> -</tr> +<table> <tr> <th colspan="5">Columns Renamed</th> </tr> @@ -576,31 +548,14 @@ the true offset is undefined. <p>As a final example, here’s the complete history for Hawaii:</p> -<table> -<tr> - <th colspan="6">Relevant Excerpts from the US Rules</th> -</tr> -<tr> - <td colspan="6"> - <table class="rule"> - <tr><td style="border:none;text-align:left"> -<pre class="td"> +<pre># Relevant Excerpts from the US Rules</th> #Rule NAME FROM TO - IN ON AT SAVE LETTER/S Rule US 1918 1919 - Oct lastSun 2:00 0 S Rule US 1942 only - Feb 9 2:00 1:00 W # War Rule US 1945 only - Aug 14 23:00u 1:00 P # Peace Rule US 1945 only - Sep lastSun 2:00 0 S -</pre> - </td></tr></table></td> -</tr> -<tr> - <th colspan="6">The Zone Record</th> -</tr> -<tr> - <td colspan="6"> - <table class="rule"> - <tr><td style="border:none;text-align:left"> -<pre class="td"> + +# The Zone Record #Zone NAME STDOFF RULES FORMAT [UNTIL] Zone Pacific/Honolulu -10:31:26 - LMT 1896 Jan 13 12:00 -10:30 - HST 1933 Apr 30 2:00 @@ -608,8 +563,7 @@ Zone Pacific/Honolulu -10:31:26 - LMT 1896 Jan 13 12:00 -10:30 US H%sT 1947 Jun 8 2:00 -10:00 - HST </pre> - </td></tr></table></td> -</tr> +<table> <tr> <th colspan="6">What We Infer</th> </tr> diff --git a/tz-link.html b/tz-link.html index ba10a68b..5e941a8d 100644 --- a/tz-link.html +++ b/tz-link.html @@ -3,8 +3,11 @@ <head> <title>Time zone and daylight saving time data</title> <meta charset="UTF-8"> +<meta name="viewport" content="width=device-width, initial-scale=1"> <style> -pre {margin-left: 2em; white-space: pre-wrap;} +dd {margin-left: 1.3rem;} +pre {margin-left: 1.3rem; overflow: auto;} +ul {padding-left: 1.3rem;} </style> </head> <body> -- 2.51.0

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Re: [PROPOSED] Mention -Dst_ctim=M in CFLAGS
by Paul Eggert Dec. 11, 2025

Dec. 11, 2025

On 2025-12-11 22:08, Robert Elz wrote: > Prior to this (since inception) we (everything BSD derived) had > st_ctimespec ... you might want to give an example of an actual use > of -Dst_ctim=M and that might be a useful one to use, as it was so > common Thanks, good suggestion. Come to think of it, it's probably clearer to give only the st_ctimespec example and let any (probably zero) builders for obscure OS versions deduce the more-general case. I installed the attached further proposed patch.

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[PROPOSED] Mention -Dst_ctim=M in CFLAGS
by Paul Eggert Dec. 11, 2025

Dec. 11, 2025

* Makefile: Add comment about using -Dst_ctim=M in CFLAGS. As far as I know this matters only on POSIXish platforms so old that they’re no longer supported by their suppliers, e.g., FreeBSD 8.4 (2013), old NetBSD, old UnixWare. --- Makefile | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/Makefile b/Makefile index eda8d53d..09f20100 100644 --- a/Makefile +++ b/Makefile @@ -284,8 +284,10 @@ LDLIBS= # -DHAVE_STRDUP=0 if your system lacks the strdup function # -DHAVE_STRNLEN=0 if your system lacks the strnlen function+ # -DHAVE_STRTOLL=0 if your system lacks the strtoll function+ -# -DHAVE_STRUCT_STAT_ST_CTIM=0 if struct stat lacks a member st_ctim -# and code should use st_ctime instead+ +# -DHAVE_STRUCT_STAT_ST_CTIM=0 if struct stat lacks a status-change member +# of type struct timespec, so code should use st_ctime instead; +# but if the status-change member is called M rather than st_ctim, +# use -Dst_ctim=M instead (default is guessed)+ # -DHAVE_STRUCT_TIMESPEC=0 if your system lacks struct timespec+ # -DHAVE_SYMLINK=0 if your system lacks the symlink function # -DHAVE_SYS_STAT_H=0 if <sys/stat.h> does not work* -- 2.51.0

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