- tz - lists.iana.org

Response to informal TZ database appeal
by Murray S. Kucherawy Sept. 22, 2021

Sept. 22, 2021

Colleagues, I am an IETF Area Director currently appointed to the Applications and Real Time (ART) area. On June 21, 2021, the ART Area Directors (ADs) received a request from Mr. Stephen Colebourne for intervention regarding a change made to the time zone database. I apologize for the delay in this response. The management of the time zone database is new to me and I wanted to ensure I had done a proper review with as much context as I could discover. Despite what I've learned, I may get some terminology below wrong; apologies if so, and I'm happy to be corrected. I take this to have been an informal appeal under the second step of RFC 6557 Section 5, which prescribes a public discussion with the participation of the ART ADs. As this was our first contact about this matter, I did not interpret the second step as having been completed, and thus this was not an appeal under the third step, which is a formal appeal to the full IESG with prescriptive results. That step, or indeed action under Section 4, remains available to you. This is a shortened version of a much longer discussion document that I have forwarded to the IESG for its reference should further appeals be lodged. Note that since this is being taken under the informal second step, nothing I say here is prescriptive. For context, RFC 6557 (also known as BCP 175) is the only normative document in force. The "theory.html" document is relevant but not normative; it has recorded an evolving set of guiding principles for the time zone database for decades, and they are maintained in the same repository as the data now in dispute. That document has been visible, and subject to discussion and proposed revisions by the community. In summary, I do not believe there is relief to be found for the instant complaint in RFC 6557. There appear to be three points comprising the complaint. Taking them in turn and citing from the message Mr. Colbourne posted to the list on June 3: (a) I contend that to date, the TZ coordinator has not actively shown any serious willingness to accept that the proposed changes are unacceptable to a significant segment of tzdb users. As such, the coordinator has not taken into account the views of the mailing list. I disagree. The TZ mailing list archive is testimonial to the contrary: The TZ Coordinator has engaged in good faith in several subsequent threads on the topic after the change was made, and has proposed other workarounds to accomplish the original goal while attempting to address the objections raised. RFC 6557 says, “... but SHOULD take into account views expressed on the mailing list.” ("SHOULD" is defined in RFC 2119.) This compels the TZ Coordinator to follow the community’s consensus, unless she/he fully understands the implications of not doing so. It is evident to me that in this case, that understanding exists. Therefore it is within the TZ Coordinator’s discretion to proceed. (b) I also contend that the "cleanup" being proposed is not within the charter of the project. Point 1 refers to new zones, thus is not applicable. Point 2 refers to correcting historical inaccuracies, yet it is clear that the proposed change *adds* historical inaccuracies. Point 3 refers to changes, but only in terms that reflect what people in the relevant location would have considered the time zone to have been, yet clearly the proposed change does not do that. No part of the charter permits the coordinator to willfully harm the database, nor to merge timezone regions, nor to increase the number of historical inaccuracies. Again, I disagree. It is worth noting at this point that RFC 6557 is over ten years old. As I reviewed it I became convinced that it, for better or worse, was written in the context of believing that the primary thing that needed to be sustained by the database is accurate time zone calculations as of 1970; aesthetics and "geopolitical" matters were a secondary consideration (if they were considered important at all). While I am sympathetic to the notion that this change may be disruptive to software or other agents that consume only the basic time zone data rather than the alternative representations also available, or may aggravate consumers on a personal level, I do not believe RFC 6557 provides a basis for demanding the change be reverted given my observation above. (c) Justifications for the proposed change based on "consistency" or "politics" are not rooted in the charter of tzdb and should be considered null and void. I disagree. I found no evidence of "political" motivation. If "consistency" is not an acceptable justification, I find it curious that the theory document has not been challenged in the years since the relevant guidelines in it became stable. I have some recommendations for additional paths forward to consider, apart from further action under Sections 4 and 5 of RFC 6557: On the topic of consensus, the IETF published RFC 7282 some years ago, which describes its view of what “consensus” means in our context. It is not a governing document, but may be informative for future discussions or operation of the TZ mailing list. It is clear that in the years since RFC 6557 was published, consumers of this database have come to rely on it for particular local representations of time zones. Mr. Colebourne refers to this as an important “geopolitical” aspect of the database and asserts that the removal of the data implemented by this change will be disruptive to these consumers, so much so that he predicts this will necessitate a forking of the database, with that set of consumers following the fork. This is far from an ideal outcome, and naturally I strongly recommend that this not be how this matter is resolved by those dissatisfied with this (or any other) outcome. Experience has shown that a forked software or data project will always diverge, even with well-intentioned management of the fork to avoid such a delta from forming. Thus, such action could be enormously disruptive to the community. It is furthermore unlikely that the fork will enjoy the same level of oversight, meticulous curation of the data, resolution of disputes, vetting of proposed changes, etc., with any assured longevity. I therefore struggle to see how such action serves anyone in the long term. In any event, and perhaps most importantly, there is the matter of the tension between what the database was originally meant to be for and how people are now consuming it. This clearly cannot be ignored. I propose the community review both RFC 6557 and the “theory” document, giving careful consideration to the principles in each and their respective impacts, and also careful consideration to how the use of this database has evolved, and propose revising either or both to reflect current usage or desired management principles. The IETF has a procedure for revising its process documents (i.e., BCPs) from time to time when the community needs something different, and it would seem that may be the case here. I will be happy to initiate that process within the IETF if a critical mass exists to take up that work. Of note, there are points in the “theory” document that appear to lack supporting language. For example, “annoyingly large” appears to be a subjective criterion, not a technical one. That is, it is unclear what technical or process degradation, if any, is caused by these extra records, so the relevance of this point is not obvious, and therefore it is not clear why this is an important guideline to have in a technical specification. Also of note, I find the “consensus on the ground” requirement of RFC 6557 is probably in need of revision or, at a minimum, clarification. It is apparent that the intent there is to assure quality service to the local communities affected by change, but it includes no practical guidance as to how to do so. Finally, I believe your next formal steps under RFC 6557, should you wish to press the issue, will be one or both of the following: (a) A formal appeal under step 3 of Section 5, which should be addressed to iesg(a)ietf.org stating clearly that this is the formal appeal; or (b) An informal request for the assistance of the ART Area Directors to reach consensus on a candidate under Section 4, which can be addressed to art-ads(a)ietf.org or to me directly. -MSK, ART Area Director

3 3

Replacing the TZ Coordinator
by SM Sept. 22, 2021

Sept. 22, 2021

Hi Stephen, On Tue, Sep 21, 2021 at 10:42:47PM +0100, Stephen Colebourne via tz wrote: >Is there consensus on the list that a change is >required? >Is there a candidate willing to take on the role of TZ Coordinator? My reading of the debate is that a change is being requested because of a dispute about a decision to merge a large number of time zones. Section 5 of RFC 6557 provides a resolution path in case such a dispute arises. In my opinion, it would be premature to invoke Section 4. Regards, -sm

1 0

Undoing the effect of the new alike-since-1970 patch
by Paul Eggert Sept. 21, 2021

Sept. 21, 2021

There's been a clear need expressed to support tzdb users who would rather not deal with the effects of the recently-proposed alike-since-1970 patch. On the other hand there are also fairness and guideline-oriented reasons for the patch, which was originally discussed and installed with more than our usual care and review. Because of the extensive followup discussions I don't see how a single version could be appealing to both sides of this disagreement. So I propose we add a Makefile or similar build-time option to let tzdb users have it either way. Set the flag one way, and it will be as if the recently-proposed changes did not occur. Set it the other way, and you'll get the changes. This will be similar to our vanguard/rearguard support, which helped address a similar disagreement back in 2018. We could even control things via the existing vanguard/rearguard build-time option; that might be simpler. If you have ideas about what the the option's specific effects should be, please let me know. If there is support for this idea, I expect to be able to implement this option soon, in plenty of time before any urgent change due to a real-world rule change arrives. Like most compromises, I expect this approach to not be entirely satisfactory to anybody. However, I hope it helps us move forward together.

15 39

Pacific/Apia no DST from 25/Sep/2021
by Geoffrey D. Bennett Sept. 20, 2021

Sept. 20, 2021

Hi there, tzdata 2021a has Pacific/Apia starting DST 26/Sep/2021 at 3am: # zdump -v Pacific/Apia | grep 2021 Pacific/Apia Sat Apr 3 13:59:59 2021 UT = Sun Apr 4 03:59:59 2021 +14 isdst=1 gmtoff=50400 Pacific/Apia Sat Apr 3 14:00:00 2021 UT = Sun Apr 4 03:00:00 2021 +13 isdst=0 gmtoff=46800 Pacific/Apia Sat Sep 25 13:59:59 2021 UT = Sun Sep 26 02:59:59 2021 +13 isdst=0 gmtoff=46800 Pacific/Apia Sat Sep 25 14:00:00 2021 UT = Sun Sep 26 04:00:00 2021 +14 isdst=1 gmtoff=50400 But according to https://www.facebook.com/MCILSamoa/posts/1666781486865573 and https://www.mcil.gov.ws/storage/2021/09/MCIL-Scan_20210920_120553.pdf DST has been cancelled for this year. Thanks, Geoffrey.

2 1

[PROPOSED] Fix ambiguous leapsecs by rolling up to a minute
by Paul Eggert Sept. 18, 2021

Sept. 18, 2021

This fixes a longstanding ambiguity in the output of localtime in oddball timezones where a positive leap second occurs when the UTC offset is not a multiple of 60 seconds. See NEWS for details. * NEWS: Describe fix. * localtime.c (timesub): Use "??:??:60" at the end of the localtime minute containing the leap second, even when the second marked "??:??:60" is not itself a leap second. This avoids ambiguity in localtime output, at the cost of having the localtime leap second occur up to a minute away from the UTC leap second when the UTC offset is not a multiple of 60 seconds. * tzfile.5: Document the fixed and unfixed behaviors. --- NEWS | 18 ++++++++++++++++++ localtime.c | 22 +++++++++++++--------- tzfile.5 | 12 ++++++++++++ 3 files changed, 43 insertions(+), 9 deletions(-) diff --git a/NEWS b/NEWS index 1bf9cf3..6a77932 100644 --- a/NEWS +++ b/NEWS @@ -109,6 +109,24 @@ Unreleased, experimental changes transition in the table, or when handling far-future timestamps in slim TZif files lacking leap seconds. + Fix localtime misbehavior involving positive leap seconds in a + timezone with a UTC offset that is not on a minute boundary. + (No such timezone exists in tzdb, luckily.) Without the fix, + the timestamp was ambiguous during a positive leap second. + With the fix, the localtime leap second appears at the end of the + localtime minute containing the UTC second just before the UTC + leap second, which means leapseconds roll slightly in these + oddball timezones. Here is how the fix affects timestamps in a + timezone with UTC offset +01:23:45 and with a positive leap second + 78796801 (1972-06-30 23:59:60 UTC): + + time_t without the fix with the fix + 78796800 1972-07-01 01:23:45 1972-07-01 01:23:45 + 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. diff --git a/localtime.c b/localtime.c index 88fd35d..6a687d7 100644 --- a/localtime.c +++ b/localtime.c @@ -1681,20 +1681,23 @@ timesub(const time_t *timep, int_fast32_t offset, register time_t tdays; register const int * ip; register int_fast32_t corr; - register bool hit; register int i; int_fast32_t idays, rem, dayoff, dayrem; time_t y; + /* If less than SECSPERMIN, the number of seconds since the + most recent positive leap second; otherwise, do not add 1 + to localtime tm_sec because of leap seconds. */ + time_t secs_since_posleap = SECSPERMIN; + corr = 0; - hit = false; i = (sp == NULL) ? 0 : sp->leapcnt; while (--i >= 0) { lp = &sp->lsis[i]; if (*timep >= lp->ls_trans) { corr = lp->ls_corr; - hit = (*timep == lp->ls_trans - && (i == 0 ? 0 : lp[-1].ls_corr) < corr); + if ((i == 0 ? 0 : lp[-1].ls_corr) < corr) + secs_since_posleap = *timep - lp->ls_trans; break; } } @@ -1761,11 +1764,12 @@ timesub(const time_t *timep, int_fast32_t offset, tmp->tm_hour = rem / SECSPERHOUR; rem %= SECSPERHOUR; tmp->tm_min = rem / SECSPERMIN; - /* - ** A positive leap second requires a special - ** representation. This uses "... ??:59:60" et seq. - */ - tmp->tm_sec = rem % SECSPERMIN + hit; + tmp->tm_sec = rem % SECSPERMIN; + + /* Use "... ??:??:60" at the end of the localtime minute containing + the second just before the positive leap second. */ + tmp->tm_sec += secs_since_posleap <= tmp->tm_sec; + ip = mon_lengths[isleap(y)]; for (tmp->tm_mon = 0; idays >= ip[tmp->tm_mon]; ++(tmp->tm_mon)) idays -= ip[tmp->tm_mon]; diff --git a/tzfile.5 b/tzfile.5 index ec78689..4a88b75 100644 --- a/tzfile.5 +++ b/tzfile.5 @@ -279,6 +279,10 @@ the purpose of skipping over them. Readers should calculate the total lengths of the headers and data blocks and check that they all fit within the actual file size, as part of a validity check for the file. +.PP +When a positive leap second occurs, readers should append a 60th +second to the local minute containing the second just before the leap +second. .SS Common interoperability issues This section documents common problems in reading or writing TZif files. Most of these are problems in generating TZif files for use by @@ -398,6 +402,14 @@ thus swapping standard and daylight saving time. Although this workaround misidentifies which part of the year uses daylight saving time, it records UT offsets and time zone abbreviations correctly. +.IP * +Some readers generate ambiguous timestamps for positive leap seconds +that occur when the UTC offset is not a multiple of 60 seconds. +For example, in a timezone with UTC offset +01:23:45 and with +a positive leap second 78796801 (1972-06-30 23:59:60 UTC), they +map both 78796800 and 78796801 to 01:23:45 local time the next day +instead of mapping the latter to 01:23:46, and they map 78796815 to +01:23:59 instead of to 01:23:60. .PP Some interoperability problems are reader bugs that are listed here mostly as warnings to developers of readers. -- 2.31.1

4 11

[PROPOSED] Match RFC 8536bis-01 better
by Paul Eggert Sept. 18, 2021

Sept. 18, 2021

* NEWS: Mention this. * tzfile.5: The draft RFC 8536bis-01 came out today; match its wording better. --- NEWS | 5 +++++ tzfile.5 | 20 +++++++++++--------- 2 files changed, 16 insertions(+), 9 deletions(-) diff --git a/NEWS b/NEWS index 00dea3c..e5f5e90 100644 --- a/NEWS +++ b/NEWS @@ -182,6 +182,11 @@ Unreleased, experimental changes 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/>. + Release 2021a - 2021-01-24 10:54:57 -0800 diff --git a/tzfile.5 b/tzfile.5 index b1932bd..dd42660 100644 --- a/tzfile.5 +++ b/tzfile.5 @@ -152,13 +152,14 @@ Each pair denotes one leap second, either positive or negative, except that if the last pair has the same correction as the previous one, the last pair denotes the leap second table's expiration time. Each leap second is at the end of a UTC calendar month. -The first leap second is positive if and only if its correction is positive, -and the correction for each leap second after the first differs +The first leap second has a nonnegative occurrence time, +and is a positive leap second if and only if its correction is positive; +the correction for each leap second after the first differs from the previous leap second by either 1 for a positive leap second, or \-1 for a negative leap second. If the leap second table is empty, the leap-second correction is zero for all timestamps; -otherwise, for timestamps before the first correction time, +otherwise, for timestamps before the first occurrence time, the leap-second correction is zero if the first pair's correction is 1 or \-1, and is unspecified otherwise (which can happen only in files truncated at the start). @@ -255,11 +256,12 @@ any data that extends beyond the calculated end of the version .PP Other than version 1, writers should generate the lowest version number needed by a file's data. -For example, a writer should generate a version 3 file -if its leap second table neither expires nor is truncated at the start -and so does not use version 4 features, but +For example, a writer should generate a version 4 file +only if its leap second table either expires or is truncated at the start. +Likewise, a writer not generating a version 4 file +should generate a version 3 file only TZ string extensions are necessary to accurately -model transition times so the file does need version 3 features. +model transition times. .PP The sequence of time changes defined by the version 1 header and data block should be a contiguous sub-sequence @@ -433,9 +435,9 @@ abbreviations correctly. Some readers generate ambiguous timestamps for positive leap seconds that occur when the UTC offset is not a multiple of 60 seconds. For example, in a timezone with UTC offset +01:23:45 and with -a positive leap second 78796801 (1972-06-30 23:59:60 UTC), they +a positive leap second 78796801 (1972-06-30 23:59:60 UTC), some readers will map both 78796800 and 78796801 to 01:23:45 local time the next day -instead of mapping the latter to 01:23:46, and they map 78796815 to +instead of mapping the latter to 01:23:46, and they will map 78796815 to 01:23:59 instead of to 01:23:60. This has not yet been a practical problem, since no civil authority has observed such UTC offsets since leap seconds were -- 2.30.2

2 2

[PROPOSED] Improve leap second table truncation doc
by Paul Eggert Sept. 16, 2021

Sept. 16, 2021

* NEWS: Mention possible successor to RFC 8536, and relaxation on TZif reader’s restriction on gaps between leaps. * tzfile.5: Improve wording on leap second expiration. Specify correction before truncated leap second table more accurately, given how localtime.c behaves; for example, the first leap second is considered to be positive if and only if its correction is positive. Say what to do after leap second table expires. Add TZ="XXX3EDT4,0/0,J365/23" example. Say that positive leap seconds not at end of localtime minute have not been a practical problem yet. * tzfile.5, zic.8: Use \- (current font minus) instead of \(mi (math font minus). --- NEWS | 6 ++++- tzfile.5 | 77 ++++++++++++++++++++++++++++++++++++++------------------ zic.8 | 2 +- 3 files changed, 58 insertions(+), 27 deletions(-) diff --git a/NEWS b/NEWS index cc69995..00dea3c 100644 --- a/NEWS +++ b/NEWS @@ -86,7 +86,8 @@ Unreleased, experimental changes 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. + 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 @@ -98,6 +99,9 @@ Unreleased, experimental changes 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. diff --git a/tzfile.5 b/tzfile.5 index bab6390..b1932bd 100644 --- a/tzfile.5 +++ b/tzfile.5 @@ -142,16 +142,26 @@ pairs of four-byte values, written in network byte order; the first value of each pair gives the nonnegative time (as returned by .BR time (2)) -at which a leap second occurs; +at which a leap second occurs or at which the leap second table expires; the second is a signed integer specifying the correction, which is the .I total number of leap seconds to be applied during the time period starting at the given time. -The pairs of values are sorted in ascending order by time. -Each transition is for one leap second, either positive or negative; -transitions always separated by at least 28 days minus 1 second. -The first entry's correction is +1 (or \(mi1, for a hypothetical leap -second table where the first leap second was negative). +The pairs of values are sorted in strictly ascending order by time. +Each pair denotes one leap second, either positive or negative, +except that if the last pair has the same correction as the previous one, +the last pair denotes the leap second table's expiration time. +Each leap second is at the end of a UTC calendar month. +The first leap second is positive if and only if its correction is positive, +and the correction for each leap second after the first differs +from the previous leap second by either 1 for a positive leap second, +or \-1 for a negative leap second. +If the leap second table is empty, the leap-second correction is zero +for all timestamps; +otherwise, for timestamps before the first correction time, +the leap-second correction is zero if the first pair's correction is 1 or \-1, +and is unspecified otherwise (which can happen only in files +truncated at the start). .IP * .B tzh_ttisstdcnt standard/wall indicators, each stored as a one-byte boolean; @@ -201,7 +211,7 @@ POSIX-TZ-environment-variable-style string for use in handling instants after the last transition time stored in the file or for all instants if the file has no transitions. The POSIX-style TZ string is empty (i.e., nothing between the newlines) -if there is no POSIX representation for such instants. +if there is no POSIX-style representation for such instants. If nonempty, the POSIX-style TZ string must agree with the local time type after the last transition time if present in the eight-byte data; for example, given the string @@ -225,8 +235,8 @@ January 1 at 00:00 and ends December 31 at 24:00 plus the difference between daylight saving and standard time. .SS Version 4 format For version-4-format TZif files, -the first leap second transition can have a correction that is neither -+1 nor \(mi1, to support TZif files with reduced timestamp range. +the first leap second record can have a correction that is neither ++1 nor \-1, to represent truncation of the TZif file at the start. Also, if two or more leap second transitions are present and the last entry's correction equals the previous one, the last entry denotes the expiration of the leap second table instead of a leap second; @@ -237,32 +247,37 @@ the added leap seconds will change how post-expiration timestamps are treated. Future changes to the format may append more data. .PP Version 1 files are considered a legacy format and -should be avoided, as they do not support transition +should not be generated, as they do not support transition times after the year 2038. -Readers that only understand Version 1 must ignore +Readers that understand only Version 1 must ignore any data that extends beyond the calculated end of the version 1 data block. .PP Other than version 1, writers should generate the lowest version number needed by a file's data. For example, a writer should generate a version 3 file -if the file does not contain a truncated leap second table +if its leap second table neither expires nor is truncated at the start and so does not use version 4 features, but TZ string extensions are necessary to accurately model transition times so the file does need version 3 features. .PP The sequence of time changes defined by the version 1 -header and data block should be a contiguous subsequence +header and data block should be a contiguous sub-sequence of the time changes defined by the version 2+ header and data block, and by the footer. This guideline helps obsolescent version 1 readers agree with current readers about timestamps within the -contiguous subsequence. It also lets writers not +contiguous sub-sequence. It also lets writers not supporting obsolescent readers use a .B tzh_timecnt of zero in the version 1 data block to save space. .PP +When a TZif file contains a leap second table expiration +time, TZif readers should either refuse to process +post-expiration timestamps, or process them as if the expiration +time did not exist (possibly with an error indication). +.PP Time zone designations should consist of at least three (3) and no more than six (6) ASCII characters from the set of alphanumerics, @@ -272,7 +287,7 @@ and This is for compatibility with POSIX requirements for time zone abbreviations. .PP -When reading a version 2+ file, readers +When reading a version 2 or higher file, readers should ignore the version 1 header and data block except for the purpose of skipping over them. .PP @@ -306,7 +321,7 @@ design goal has been that a reader can successfully use a TZif file even if the file is of a later TZif version than what the reader was designed for. When complete compatibility was not achieved, an attempt was -made to limit glitches to rarely-used timestamps, and to allow +made to limit glitches to rarely used timestamps and allow simple partial workarounds in writers designed to generate new-version data useful even for older-version readers. This section attempts to document these compatibility issues and @@ -323,24 +338,33 @@ version 2+ data even if the reader's native timestamps have only 32 bits. .IP * Some readers designed for version 2 might mishandle -timestamps after a version 3 file's last transition, because +timestamps after a version 3 or higher file's last transition, because they cannot parse extensions to POSIX in the TZ-like string. As a partial workaround, a writer can output more transitions than necessary, so that only far-future timestamps are mishandled by version 2 readers. .IP * Some readers designed for version 2 do not support -permanent daylight saving time, e.g., a TZ string +permanent daylight saving time with transitions after 24:00 +\(en e.g., a TZ string .q "EST5EDT,0/0,J365/25" -denoting permanent Eastern Daylight Time (\-04). -As a partial workaround, a writer can substitute standard time -for the next time zone east, e.g., +denoting permanent Eastern Daylight Time +(\-04). +As a workaround, a writer can substitute standard time +for two time zones east, e.g., +.q "XXX3EDT4,0/0,J365/23" +for a time zone with a never-used standard time (XXX, \-03) +and negative daylight saving time (EDT, \-04) all year. +Alternatively, +as a partial workaround a writer can substitute standard time +for the next time zone east \(en e.g., .q "AST4" -for permanent Atlantic Standard Time (\-04). +for permanent +Atlantic Standard Time (\-04). .IP * -Some readers designed for earlier versions reject version 4 files, -because they require complete leap second tables that do not record -expiration dates. +Some readers designed for version 2 or 3, and that require strict +conformance to RFC 8536, reject version 4 files whose leap second +tables are truncated at the start or that end in expiration times. .IP * Some readers ignore the footer, and instead predict future timestamps from the time type of the last transition. @@ -413,6 +437,9 @@ a positive leap second 78796801 (1972-06-30 23:59:60 UTC), they map both 78796800 and 78796801 to 01:23:45 local time the next day instead of mapping the latter to 01:23:46, and they map 78796815 to 01:23:59 instead of to 01:23:60. +This has not yet been a practical problem, since no civil authority +has observed such UTC offsets since leap seconds were +introduced in 1972. .PP Some interoperability problems are reader bugs that are listed here mostly as warnings to developers of readers. diff --git a/zic.8 b/zic.8 index 3149440..ea7bab9 100644 --- a/zic.8 +++ b/zic.8 @@ -550,7 +550,7 @@ using the shortest form that does not lose information, where .IR mm , and .I ss -are the hours, minutes, and seconds east (+) or west (\(mi) of UT. +are the hours, minutes, and seconds east (+) or west (\-) of UT. Alternatively, a slash (/) separates standard and daylight abbreviations. -- 2.30.2

1 0

[CfP][CalendarFest] Call for lightning talk proposals for CalendarFest 2021 - current topics in electronic calendaring
by Hans-Joerg Happel Sept. 15, 2021

Sept. 15, 2021

Hi, my apologies for being slightly off topic, but I guess this might be interesting to see some of you / related to some topics discussed on this list. Please feel also free to forward this to anybody you might have in mind, who is dealing with novel calendaring solutions and ideas and might be interested in community discussion. Thanks and best, Hans-Joerg ----- CalendarFest is a novel (virtual) event, which wants to let users and developers of (electronic) calendar applications, servers, and related groupware systems, share experiences and discuss novel ideas. CalendarFest will take place *18th of October*, 02:30h PM UTC virtually via Zoom, and is held in conjunction with the CalConnect virtual conference <https://www.calconnect.org/events/calconnect-virtual-conference-autumn-2021>. Lightning talks People who wish to discuss or present certain topics are invited to submit a *proposal for lightning talks*. Lightning Talk presentations will be a maximum of 15-20 minutes each. Presenters may use slides, but these must be submitted to the Lightning Talks chair a few days before the presentation. Proposals Lightning Talk proposals must be submitted in PDF format. The proposal is limited to 1 page, 500 words max. The full proposal contains a title, an abstract (maximum 250 words) and a description where you should explain your talk in more detail. It will be helpful for reviewers to know why you are excited about the topic, and why you think others will be interested too. Outline how you plan to present your topic. The proposal also may contain a link to a website with more information. Possible Topics * Enterprise calendaring * Public calendaring * Calendaring and Semantic Web/Linked Data * Calendar Interoperability and Migration * Calendaring Security and Privacy by Design * Personal information management (PIM) and groupware * AI in calendaring * Calendaring and scheduling in IoT * Mobile calendaring * Calendar visualization, user experience and usability * Novel applications of calendars * Calendaring standards (vCard, iCal, CalDAV, CardDAV, JMAP) * Date/Time representations and Time zones * Business models for calendaring and groupware Program committee Submissions will be reviewed by the following members of the CalConnect TC-CLIENT technical committee: * Mike Douglass * Hans-Jörg Happel * Alex Nimmervoll Timeline * Send your lightning talk proposal to *calendarfest(a)calconnect.org <mailto:calendarfest@calconnect.org>* until *October, 4th* * You will receive a notification of acceptance or reject by October, 11th * CalendarFest will take place on October, 18th Participation Participation at CalendarFest will be free for presenters of accepted talks. Other participants need to register <https://www.calconnect.org/news/2021/09/02/registration-open-october-2021-c…> for a small organizational fee, which also allows for participation at the “colocated” CalConnect Virtual Conference. About CalConnect (www.calconnect.org <http://www.calconnect.org>) is a non-profit partnership between vendors and users of collaboration systems and tools, in particular calendaring and scheduling. CalConnect members convene regularly to discuss and develop standards for electronic calendaring and related topics. The goal of CalendarFest, which is held in conjunction with the CalConnect Virtual Conference, is to provide an interdisciplinary discussion space for current topics in electronic calendaring from different perspectives. *CalendarFest website: https://public.calconnect.org/CalendarFest/*

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[PROPOSED] Don't mistruncate TZif files at leap seconds
by Paul Eggert Sept. 14, 2021

Sept. 14, 2021

Without this fix, zic mishandles the command ‘zic -L leapseconds -r @1706745601 etcetera’ when ‘leapseconds’ is generated from the test data file mentioned in: https://mm.icann.org/pipermail/tz/2021-September/030385.html The resulting, incorrect TZif file causes ‘TZ=Etc/GMT date -r 1706745601’ to output "Thu Feb 1 00:00:01 GMT 2024" instead of the correct "Thu Feb 1 00:00:00 GMT 2024", because localtime misinterprets the leap second entry at 1706745601 to be a positive instead of a negative leap second. * NEWS: Mention the fix. * zic.c (limitrange): When omitting leading leap seconds, do not output a leap second table that starts with a positive leap second with a nonpositive correction (or with a negative leap second with a positive correction) as that will confuse TZif readers into thinking the positive leap second is negative or vice versa. Instead, keep otherwise-unnecessary leading leap seconds to avoid the confusion. --- NEWS | 6 ++++++ zic.c | 14 ++++++++++++-- 2 files changed, 18 insertions(+), 2 deletions(-) diff --git a/NEWS b/NEWS index 62a7ba2..9983f11 100644 --- a/NEWS +++ b/NEWS @@ -137,6 +137,12 @@ Unreleased, experimental changes 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. diff --git a/zic.c b/zic.c index b06ef66..c6feb8b 100644 --- a/zic.c +++ b/zic.c @@ -1972,12 +1972,22 @@ limitrange(struct timerange r, bool locut, zic_t lo, zic_t hi, r.base++; } - /* Omit as many leap seconds < LO as possible, such that the first - leap second in the truncated list is <= LO. */ + /* Omit as many initial leap seconds as possible, such that the + first leap second in the truncated list is <= LO, and is a + positive leap second if and only if it has a positive correction. + This supports common TZif readers that assume that the first leap + second is positive if and only if its correction is positive. */ while (1 < r.leapcount && trans[r.leapbase + 1] <= lo) { r.leapcount--; r.leapbase++; } + while (0 < r.leapbase + && ((corr[r.leapbase - 1] < corr[r.leapbase]) + != (0 < corr[r.leapbase]))) { + r.leapcount++; + r.leapbase--; + } + /* Omit ordinary and leap second transitions greater than HI + 1. */ if (hi < ZIC_MAX) { -- 2.30.2

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Re: [tz] No leap second on 2021-12-31
by Kerry Shetline Sept. 14, 2021

Sept. 14, 2021

What’s interesting is that the Earth is undergoing an odd span of time during which it has been spinning a bit faster instead of slowing down. If this keeps up, not only will it be a while until we see another leap second, but in a few years we might experience the first negative leap second, where a second is dropped from the end of the last minute just before 00:00 UTC. > Per IERS, Bulletin C 62 (2021-07-05) > https://hpiers.obspm.fr/iers/bul/bulc/bulletinc.62 > > ?and forwarded below. > > A patch updating leap-seconds.list from NIST is attached, and is installed > in the development repository. > > -- > Tim Parenti

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