update to 2025a

Changes to code

strftime %s now generates the correct numeric string even when the
represented number does not fit into time_t. This is better than
generating the num

update to 2025a

Changes to code

strftime %s now generates the correct numeric string even when the
represented number does not fit into time_t. This is better than
generating the numeric equivalent of (time_t) -1, as strftime did
in TZDB releases 96a (when %s was introduced) through 2020a and in
releases 2022b through 2024b. It is also better than failing and
returning 0, as strftime did in releases 2020b through 2022a.

strftime now outputs an invalid conversion specifier as-is,
instead of eliding the leading '%', which confused debugging.

An invalid TZ now generates the time zone abbreviation "-00", not
"UTC", to help the user see that an error has occurred. (Thanks
to Arthur David Olson for suggesting a "wrong result".)

mktime and timeoff no longer incorrectly fail merely because a
struct tm component near INT_MIN or INT_MAX overflows when a
lower-order component carries into it.

TZNAME_MAXIMUM, the maximum number of bytes in a proleptic TZ
string's time zone abbreviation, now defaults to 254 not 255.
This helps reduce the size of internal state from 25480 to 21384
on common platforms. This change should not be a problem, as
nobody uses such long "abbreviations" and the longstanding tzcode
maximum was 16 until release 2023a. For those who prefer no
arbitrary limits, you can now specify TZNAME_MAXIMUM values up to
PTRDIFF_MAX, a limit forced by C anyway; formerly tzcode silently
misbehaved unless TZNAME_MAXIMUM was less than INT_MAX.

tzset and related functions no longer leak a file descriptor if
another thread forks or execs at about the same time and if the
platform has O_CLOFORK and O_CLOEXEC respectively. Also, the
functions no longer let a TZif file become a controlling terminal.

'zdump -' now reads TZif data from /dev/stdin.
(From a question by Arthur David Olson.)

show more ...

libc/locale: Nix needless size_t casts.

No functional change intended. No binary change to aarch64 libc.

Prompted by code inspection around PR lib/58319.

Revert this part:

strftime %s now uses tm_gmtoff if available. (Problem and draft
patch reported by Dag-Erling Smørgrav.)

of the tzcode2924a update. It is bogus. The "problem" is/was a simpl

Revert this part:

strftime %s now uses tm_gmtoff if available. (Problem and draft
patch reported by Dag-Erling Smørgrav.)

of the tzcode2924a update. It is bogus. The "problem" is/was a simple
misunderstanding of what strftime(%s) is intended to output. The "fix"
breaks it.

show more ...

Sync with tzcode2024a:
Release 2024a - 2024-02-01 09:28:56 -0800

Changes to code

The FROM and TO columns of Rule lines can no longer be "minimum"
or an abbreviation of "minimum", because

Sync with tzcode2024a:
Release 2024a - 2024-02-01 09:28:56 -0800

Changes to code

The FROM and TO columns of Rule lines can no longer be "minimum"
or an abbreviation of "minimum", because TZif files do not support
DST rules that extend into the indefinite past - although these
rules were supported when TZif files had only 32-bit data, this
stopped working when 64-bit TZif files were introduced in 1995.
This should not be a problem for realistic data, since DST was
first used in the 20th century. As a transition aid, FROM columns
like "minimum" are now diagnosed and then treated as if they were
the year 1900; this should suffice for TZif files on old systems
with only 32-bit time_t, and it is more compatible with bugs in
2023c-and-earlier localtime.c. (Problem reported by Yoshito
Umaoka.)

localtime and related functions no longer mishandle some
timestamps that occur about 400 years after a switch to a time
zone with a DST schedule. In 2023d data this problem was visible
for some timestamps in November 2422, November 2822, etc. in
America/Ciudad_Juarez. (Problem reported by Gilmore Davidson.)

strftime %s now uses tm_gmtoff if available. (Problem and draft
patch reported by Dag-Erling Smørgrav.)

Changes to build procedure

The leap-seconds.list file is now copied from the IERS instead of
from its downstream counterpart at NIST, as the IERS version is
now in the public domain too and tends to be more up-to-date.
(Thanks to Martin Burnicki for liaisoning with the IERS.)

Changes to documentation

The strftime man page documents which struct tm members affect
which conversion specs, and that tzset is called. (Problems
reported by Robert Elz and Steve Summit.)

show more ...

Catch up with all the lint warnings since exit on warning was disabled.
Disable 'missing header declaration' and 'nested extern' warnings for now.

Update tzcode from 2022g to 2023c:

Release 2023c - 2023-03-28 12:42:14 -0700

Release 2023b - 2023-03-23 19:50:38 -0700

Release 2023a - 2023-03-22 12:39:33 -0700

Changes to code

You can now

Update tzcode from 2022g to 2023c:

Release 2023c - 2023-03-28 12:42:14 -0700

Release 2023b - 2023-03-23 19:50:38 -0700

Release 2023a - 2023-03-22 12:39:33 -0700

Changes to code

You can now tell tzselect local time, to simplify later choices.
Select the 'time' option in its first prompt.

You can now compile with -DTZNAME_MAXIMUM=N to limit time zone
abbreviations to N bytes (default 255). The reference runtime
library now rejects POSIX-style TZ strings that contain longer
abbreviations, treating them as UTC. Previously the limit was
platform dependent and abbreviations were silently truncated to
16 bytes even when the limit was greater than 16.

The code by default is now designed for C99 or later. To build in
a C89 environment, compile with -DPORT_TO_C89. To support C89
callers of the tzcode library, compile with -DSUPPORT_C89. The
two new macros are transitional aids planned to be removed in a
future version, when C99 or later will be required.

The code now builds again on pre-C99 platforms, if you compile
with -DPORT_TO_C89. This fixes a bug introduced in 2022f.

On C23-compatible platforms tzcode no longer uses syntax like
'static [[noreturn]] void usage(void);'. Instead, it uses
'[[noreturn]] static void usage(void);' as strict C23 requires.
(Problem reported by Houge Langley.)

The code's functions now constrain their arguments with the C
'restrict' keyword consistently with their documentation.
This may allow future optimizations.

zdump again builds standalone with ckdadd and without setenv,
fixing a bug introduced in 2022g. (Problem reported by panic.)

leapseconds.awk can now process a leap seconds file that never
expires; this might be useful if leap seconds are discontinued.

Changes to commentary

tz-link.html has a new section "Coordinating with governments and
distributors". (Thanks to Neil Fuller for some of the text.)

To improve tzselect diagnostics, zone1970.tab's comments column is
now limited to countries that have multiple timezones.

Note that leap seconds are planned to be discontinued by 2035.

show more ...

Merge in 2022g:

Although tzcode still works with C89, bugs found in recent routine
maintenance indicate that bitrot has set in and that in practice
C89 is no longer used to build tzcode.

Merge in 2022g:

Although tzcode still works with C89, bugs found in recent routine
maintenance indicate that bitrot has set in and that in practice
C89 is no longer used to build tzcode. As it is a maintenance
burden, support for C89 is planned to be removed soon. Instead,
please use compilers compatible with C99, C11, C17, or C23.

timegm, which tzcode implemented in 1989, will finally be
standardized 34 years later as part of C23, so timegm is now
supported even if STD_INSPIRED is not defined.

Fix bug in zdump's tzalloc emulation on hosts that lack tm_zone.
(Problem reported by Đoàn Trần Công Danh.)

Fix bug in zic on hosts where malloc(0) yields NULL on success.
(Problem reported by Tim McBrayer for AIX 6.1.)

Fix zic configuration to avoid linkage failures on some platforms.
(Problems reported by Gilmore Davidson and Igor Ivanov.)

Work around MS-Windows nmake incompatibility with POSIX.
(Problem reported by Manuela Friedrich.)

Port mktime and strftime to debugging platforms where accessing
uninitialized data has undefined behavior (strftime problem
reported by Robert Elz).

Check more carefully for unlikely integer overflows, preferring
C23 <stdckdint.h> to overflow checking by hand, as the latter has
had obscure bugs.

show more ...

Welcome to 2022b:

zic has a new option '-R @N' to output explicit transitions < N.
(Need suggested by Almaz Mingaleev.)

'zic -r @N' no longer outputs bad data when N < first transition.
(Problem in

Welcome to 2022b:

zic has a new option '-R @N' to output explicit transitions < N.
(Need suggested by Almaz Mingaleev.)

'zic -r @N' no longer outputs bad data when N < first transition.
(Problem introduced in 2021d and reported by Peter Krefting.)

zic now checks its input for NUL bytes and unterminated lines, and
now supports input line lengths up to 2048 (not 512) bytes.

gmtime and related code now use the abbreviation "UTC" not "GMT".
POSIX is being revised to require this.

When tzset and related functions set vestigial static variables
like tzname, they now prefer specified timestamps to unspecified ones.
(Problem reported by Almaz Mingaleev.)

zic no longer complains "can't determine time zone abbreviation to
use just after until time" when a transition to a new standard
time occurs simultanously with the first DST fallback transition.

show more ...

Change to code and documentation from 2021a -> 2021e

Release 2021e - 2021-10-21 18:41:00 -0700

Changes to code

none


Release 2021d - 2021-10-15 13:48:18 -0700

Changes to code

'zic -

Change to code and documentation from 2021a -> 2021e

Release 2021e - 2021-10-21 18:41:00 -0700

Changes to code

none


Release 2021d - 2021-10-15 13:48:18 -0700

Changes to code

'zic -r' now uses "-00" time zone abbreviations for intervals
with UT offsets that are unspecified due to -r truncation.
This implements a change in draft Internet RFC 8536bis.


Release 2021c - 2021-10-01 14:21:49 -0700

Changes to code

Fix a bug in 'zic -b fat' that caused old timestamps to be
mishandled in 32-bit-only readers (problem reported by Daniel
Fischer).

Changes to documentation

Distribute the SECURITY file (problem reported by Andreas Radke).


Release 2021b - 2021-09-24 16:23:00 -0700

Changes to maintenance procedure

The new file SECURITY covers how to report security-related bugs.

Several backward-compatibility links have been moved to the
'backward' file. These links, which range from Africa/Addis_Ababa
to Pacific/Saipan, are only for compatibility with now-obsolete
guidelines suggesting an entry for every ISO 3166 code.
The intercontinental convenience links Asia/Istanbul and
Europe/Nicosia have also been moved to 'backward'.

Changes to code

zic now creates each output file or link atomically,
possibly by creating a temporary file and then renaming it.
This avoids races where a TZ setting would temporarily stop
working while zic was installing a replacement file or link.

zic -L no longer omits the POSIX TZ string in its output.
Starting with 2020a, zic -L truncated its output according to the
"Expires" directive or "#expires" comment in the leapseconds file.
The resulting TZif files omitted daylight saving transitions after
the leap second table expired, which led to far less-accurate
predictions of times after the expiry. Although future timestamps
cannot be converted accurately in the presence of leap seconds, it
is more accurate to convert near-future timestamps with a few
seconds error than with an hour error, so zic -L no longer
truncates output in this way.

Instead, when zic -L is given the "Expires" directive, it now
outputs the expiration by appending a no-change entry to the leap
second table. Although this should work well with most TZif
readers, it does not conform to Internet RFC 8536 and some pickier
clients (including tzdb 2017c through 2021a) reject it, so
"Expires" directives are currently disabled by default. To enable
them, set the EXPIRES_LINE Makefile variable. If a TZif file uses
this new feature it is marked with a new TZif version number 4,
a format intended to be documented in a successor to RFC 8536.

zic -L LEAPFILE -r @LO no longer generates an invalid TZif file
that omits leap second information for the range LO..B when LO
falls between two leap seconds A and B. Instead, it generates a
TZif version 4 file that represents the previously-missing
information.

The TZif reader now allows the leap second table to begin with a
correction other than -1 or +1, and to contain adjacent
transitions with equal corrections. This supports TZif version 4.

The TZif reader now lets leap seconds occur less than 28 days
apart. This supports possible future TZif extensions.

Fix bug that caused 'localtime' etc. to crash when TZ was
set to a all-year DST string like "EST5EDT4,0/0,J365/25" that does
not conform to POSIX but does conform to Internet RFC 8536.

Fix another bug that caused 'localtime' etc. to crash when TZ was
set to a POSIX-conforming but unusual TZ string like
"EST5EDT4,0/0,J365/0", where almost all the year is DST.

Fix yet another bug that caused 'localtime' etc. to mishandle slim
TZif files containing leap seconds after the last explicit
transition in the table, or when handling far-future timestamps
in slim TZif files lacking leap seconds.

Fix localtime misbehavior involving positive leap seconds.
This change affects only behavior for "right" system time,
which contains leap seconds, and only if the UT offset is
not a multiple of 60 seconds when a positive leap second occurs.
(No such timezone exists in tzdb, luckily.) Without the fix,
the timestamp was ambiguous during a positive leap second.
With the fix, any seconds occurring after a positive leap second
and within the same localtime minute are counted through 60, not
through 59; their UT offset (tm_gmtoff) is the same as before.
Here is how the fix affects timestamps in a timezone with UT
offset +01:23:45 (5025 seconds) and with a positive leap second at
1972-06-30 23:59:60 UTC (78796800):

time_t without the fix with the fix
78796800 1972-07-01 01:23:45 1972-07-01 01:23:45 (leap second)
78796801 1972-07-01 01:23:45 1972-07-01 01:23:46
...
78796815 1972-07-01 01:23:59 1972-07-01 01:23:60
78796816 1972-07-01 01:24:00 1972-07-01 01:24:00

Fix an unlikely bug that caused 'localtime' etc. to misbehave if
civil time changes a few seconds before time_t wraps around, when
leap seconds are enabled.

Fix bug in zic -r; in some cases, the dummy time type after the
last time transition disagreed with the TZ string, contrary to
Internet RFC 8563 section 3.3.

Fix a bug with 'zic -r @X' when X is a negative leap second that
has a nonnegative correction. Without the fix, the output file
was truncated so that X appeared to be a positive leap second.
Fix a similar, even-less-likely bug when truncating at a positive
leap second that has a nonpositive correction.

zic -r now reports an error if given rolling leap seconds, as this
usage has never generally worked and is evidently unused.

zic now generates a POSIX-conforming TZ string for TZif files
where all-year DST is predicted for the indefinite future.
For example, for all-year Eastern Daylight Time, zic now generates
"XXX3EDT4,0/0,J365/23" where it previously generated
"EST5EDT,0/0,J365/25" or "". (Thanks to Michael Deckers for
noting the possibility of POSIX conformance.)

zic.c no longer requires sys/wait.h (thanks to spazmodius for
noting it wasn't needed).

When reading slim TZif files, zdump no longer mishandles leap
seconds on the rare platforms where time_t counts leap seconds,
fixing a bug introduced in 2014g.

zdump -v now outputs timestamps at boundaries of what localtime
and gmtime can represent, instead of the less-useful timestamps
one day after the minimum and one day before the maximum.
(Thanks to Arthur David Olson for prototype code, and to Manuela
Friedrich for debugging help.)

zdump's -c and -t options are now consistently inclusive for the
lower time bound and exclusive for the upper. Formerly they were
inconsistent. (Confusion noted by Martin Burnicki.)

Changes to build procedure

You can now compile with -DHAVE_MALLOC_ERRNO=0 to port to
non-POSIX hosts where malloc doesn't set errno.
(Problem reported by Jan Engelhardt.)

Changes to documentation

tzfile.5 better matches a draft successor to RFC 8536
<https://datatracker.ietf.org/doc/draft-murchison-rfc8536bis/01/>.

show more ...

Merge tzcode2020b (except we keep tzsetwall(3) for now for compatibility,
and we were "slim" already)

Support for zic's long-obsolete '-y YEARISTYPE' option has been
removed and, with it, so has sup

Merge tzcode2020b (except we keep tzsetwall(3) for now for compatibility,
and we were "slim" already)

Support for zic's long-obsolete '-y YEARISTYPE' option has been
removed and, with it, so has support for the TYPE field in Rule
lines, which is now reserved for compatibility with earlier zic.
These features were previously deprecated in release 2015f.
(Thanks to Tim Parenti.)

zic now defaults to '-b slim' instead of to '-b fat'.

zic's new '-l -' and '-p -' options uninstall any existing
localtime and posixrules files, respectively.

The undocumented and ineffective tzsetwall function has been
removed.

show more ...

Bring in 2020a

don't print ???, requested by kre@

Don't try to print NULL if we can't get a timezone name. First we try dst,
then we try the non-dst name and finally we just print ??? if that did not
work. This is not needed to handle the "TZ= date"

Don't try to print NULL if we can't get a timezone name. First we try dst,
then we try the non-dst name and finally we just print ??? if that did not
work. This is not needed to handle the "TZ= date" case which was crashing
before because the default timezone was not consistently initialized, but
should handle any timezone now.

show more ...

- Padding support from FreeBSD (GNU extensions)
- add '+' for the c-locale only.

Make strftime_{l,z} re-entrant and always require a non-NULL timezone to be
passed in so that we can use the current timezone in all evaluations (mktime
tzgetname). Reported by Hamilton Slye.

Update to 2018f:

Changes to code

zic now always generates TZif files where time type 0 is used for
timestamps before the first transition. This simplifies the
reading of TZif files a

Update to 2018f:

Changes to code

zic now always generates TZif files where time type 0 is used for
timestamps before the first transition. This simplifies the
reading of TZif files and should not affect behavior of existing
TZif readers because the same set of time types is used; only
their internal indexes may have changed. This affects only the
legacy zones EST5EDT, CST6CDT, MST7MDT, PST8PDT, CET, MET, and
EET, which previously used nonzero types for these timestamps.

Because of the type 0 change, zic no longer outputs a dummy
transition at time -2**59 (before the Big Bang), as clients should
no longer need this to handle historical timestamps correctly.
This reverts a change introduced in 2013d and shrinks most TZif
files by a few bytes.

zic now supports negative time-of-day in Rule and Leap lines, e.g.,
"Rule X min max - Apr lastSun -6:00 1:00 -" means the transition
occurs at 18:00 on the Saturday before the last Sunday in April.
This behavior was documented in 2018a but the code did not
entirely match the documentation.

localtime.c no longer requires at least one time type in TZif
files that lack transitions or have a POSIX-style TZ string. This
future-proofs the code against possible future extensions to the
format that would allow TZif files with POSIX-style TZ strings and
without transitions or time types.

A read-access subscript error in localtime.c has been fixed.
It could occur only in TZif files with timecnt == 0, something that
does not happen in practice now but could happen in future versions.

localtime.c no longer ignores TZif POSIX-style TZ strings that
specify only standard time. Instead, these TZ strings now
override the default time type for timestamps after the last
transition (or for all time stamps if there are no transitions),
just as DST strings specifying DST have always done.

leapseconds.awk now outputs "#updated" and "#expires" comments,
and supports leap seconds at the ends of months other than June
and December. (Inspired by suggestions from Chris Woodbury.)

Changes to documentation

New restrictions: A Rule name must start with a character that
is neither an ASCII digit nor "-" nor "+", and an unquoted name
should not use characters in the set "!$%&'()*,/:;<=>?@[\]^`{|}~".
The latter restriction makes room for future extensions (a
possibility noted by Tom Lane).

tzfile.5 now documents what time types apply before the first and
after the last transition, if any.

Documentation now uses the spelling "timezone" for a TZ setting
that determines timestamp history, and "time zone" for a
geographic region currently sharing the same standard time.

The name "TZif" is now used for the tz binary data format.

tz-link.htm now mentions the A0 TimeZone Migration utilities.
(Thanks to Aldrin Martoq for the link.)

show more ...

Merge 2018e

Changes to code

zic now accepts subsecond precision in expressions like
00:19:32.13, which is approximately the legal time of the
Netherlands from 1835 to 1937. However,

Merge 2018e

Changes to code

zic now accepts subsecond precision in expressions like
00:19:32.13, which is approximately the legal time of the
Netherlands from 1835 to 1937. However, because it is
questionable whether the few recorded uses of non-integer offsets
had subsecond precision in practice, there are no plans for tzdata
to use this feature. (Thanks to Steve Allen for pointing out
the limitations of historical data in this area.)

The code is a bit more portable to MS-Windows. Installers can
compile with -DRESERVE_STD_EXT_IDS on MS-Windows platforms that
reserve identifiers like 'localtime'. (Thanks to Manuela
Friedrich).

Changes to documentation and commentary

theory.html now outlines tzdb's extensions to POSIX's model for
civil time, and has a section "POSIX features no longer needed"
that lists POSIX API components that are now vestigial.
(From suggestions by Steve Summit.) It also better distinguishes
time zones from tz regions. (From a suggestion by Guy Harris.)

Commentary is now more consistent about using the phrase "daylight
saving time", to match the C name tm_isdst. Daylight saving time
need not occur in summer, and need not have a positive offset from
standard time.

Commentary about historical transitions in Uruguay has been expanded
with links to many relevant legal documents.
(Thanks to Tim Parenti.)

Commentary now uses some non-ASCII characters with Unicode value
less than U+0100, as they can be useful and should work even with
older editors such as XEmacs.

show more ...

Welcome to 2017c:

zic and the reference runtime now reject multiple leap seconds
within 28 days of each other, or leap seconds before the Epoch.
As a result, support for double leap seco

Welcome to 2017c:

zic and the reference runtime now reject multiple leap seconds
within 28 days of each other, or leap seconds before the Epoch.
As a result, support for double leap seconds, which was
obsolescent and undocumented, has been removed. Double leap
seconds were an error in the C89 standard; they have never existed
in civil timekeeping. (Thanks to Robert Elz and Bradley White for
noticing glitches in the code that uncovered this problem.)

zic now warns about use of the obsolescent and undocumented -y
option, and about use of the obsolescent TYPE field of Rule lines.

zic now allows unambiguous abbreviations like "Sa" and "Su" for
weekdays; formerly it rejected them due to a bug. Conversely, zic
no longer considers non-prefixes to be abbreviations; for example,
it no longer accepts "lF" as an abbreviation for "lastFriday".
Also, zic warns about the undocumented usage with a "last-"
prefix, e.g., "last-Fri".

Similarly, zic now accepts the unambiguous abbreviation "L" for
"Link" in ordinary context and for "Leap" in leap-second context.
Conversely, zic no longer accepts non-prefixes such as "La" as
abbreviations for words like "Leap".

zic no longer accepts leap second lines in ordinary input, or
ordinary lines in leap second input. Formerly, zic sometimes
warned about this undocumented usage and handled it incorrectly.

The new macro HAVE_TZNAME governs whether the tzname external
variable is exported, instead of USG_COMPAT. USG_COMPAT now
governs only the external variables "timezone" and "daylight".
This change is needed because the three variables are not in the
same category: although POSIX requires tzname, it specifies the
other two variables as optional. Also, USG_COMPAT is now 1 or 0:
if not defined, the code attempts to guess it from other macros.

localtime.c and difftime.c no longer require stdio.h, and .c files
other than zic.c no longer require sys/wait.h.

zdump.c no longer assumes snprintf. (Reported by Jonathan Leffler.)

Calculation of time_t extrema works around a bug in GCC 4.8.4
(Reported by Stan Shebs and Joseph Myers.)

zic.c no longer mistranslates formats of line numbers in non-English
locales. (Problem reported by Benno Schulenberg.)

Several minor changes have been made to the code to make it a
bit easier to port to MS-Windows and Solaris. (Thanks to Kees
Dekker for reporting the problems.)

Changes to documentation and commentary

The two new files 'theory.html' and 'calendars' contain the
contents of the removed file 'Theory'. The goal is to document
tzdb theory more accessibly.

The zic man page now documents abbreviation rules.

tz-link.htm now covers how to apply tzdata changes to clients.
(Thanks to Jorge Fábregas for the AIX link.) It also mentions MySQL.

The leap-seconds.list URL has been updated to something that is
more reliable for tzdb. (Thanks to Tim Parenti and Brian Inglis.)

show more ...

merge 2017a

welcome to 2016h

merge tzcode2016g

Sync with 2016b

Release 2015g - 2015-10-01 00:39:51 -0700

Changes affecting code

localtime no longer mishandles America/Anchorage after 2037.
(Thanks to Bradley White for reporting the bug.)

The loc

Release 2015g - 2015-10-01 00:39:51 -0700

Changes affecting code

localtime no longer mishandles America/Anchorage after 2037.
(Thanks to Bradley White for reporting the bug.)

The localtime module allows the variables 'timezone', 'daylight',
and 'altzone' to be in common storage shared with other modules,
and declares them in case the system <time.h> does not.
(Problems reported by Kees Dekker.)

On platforms with tm_zone, strftime.c now assumes it is not NULL.
This simplifies the code and is consistent with zdump.c.
(Problem reported by Christos Zoulas.)

Changes affecting documentation

The tzfile man page now documents that transition times denote the
starts (not the ends) of the corresponding time periods.
(Ambiguity reported by Bill Seymour.)

show more ...

merge 2015f

Sync with tzcode2014h