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Re: [tz] tzcode2021e: uninitialized variable in localtime.c
by Paul Eggert Oct. 27, 2021

Oct. 27, 2021

On 10/22/21 07:49, Christos Zoulas wrote: > My linter reports "prevcorr" is uninitialized in the if statement > below the comment that starts "To avoid other botches". Thanks for mentioning that. This prompted me to find an obscure bug in localtime that would cause it to access an uninitialized local variable (which is undefined behavior) in cases involving 32-bit time_t code reading malformed 64-bit data. I installed the attached patch to fix the bug, and I hope this also pacifies your linter.

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[PROPOSED] Be more generous when dealing with v1 data
by Paul Eggert Oct. 27, 2021

Oct. 27, 2021

* NEWS: Mention this. * localtime.c (tzloadbody): In version 2 and later files, do not attempt to validate the version 1 header and data block; instead, ignore them except for the purpose of skipping over them, as per a recommendation in RFC 8536 section 4. Also, when the TZif file is version 1 and we break out near the end of the loop, do so only after altering nread and memmoving any later data; this avoids having later code attempt to parse the version 1 header as if it were a TZ string. --- NEWS | 6 +++++ localtime.c | 71 +++++++++++++++++++++++++++++++---------------------- 2 files changed, 47 insertions(+), 30 deletions(-) diff --git a/NEWS b/NEWS index d4a9823..0f684f7 100644 --- a/NEWS +++ b/NEWS @@ -14,6 +14,12 @@ Unreleased, experimental changes Fix bug when 32-bit time_t code reads malformed 64-bit TZif data. (Problem reported by Christos Zoulas.) + When reading a version 2 or later TZif file, the TZif reader now + validates the version 1 header and data block only enough to skip + over them, as recommended by RFC 8536 section 4. Also, the TZif + reader no longer mistakenly attempts to parse a version 1 TZIf + file header as a TZ string. + Release 2021e - 2021-10-21 18:41:00 -0700 diff --git a/localtime.c b/localtime.c index 6d736b2..39ef6e3 100644 --- a/localtime.c +++ b/localtime.c @@ -434,35 +434,45 @@ tzloadbody(char const *name, struct state *sp, bool doextend, if (close(fid) < 0) return errno; for (stored = 4; stored <= 8; stored *= 2) { - int_fast32_t ttisstdcnt = detzcode(up->tzhead.tzh_ttisstdcnt); - int_fast32_t ttisutcnt = detzcode(up->tzhead.tzh_ttisutcnt); - int_fast64_t prevtr = -1; - int_fast32_t prevcorr; - int_fast32_t leapcnt = detzcode(up->tzhead.tzh_leapcnt); - int_fast32_t timecnt = detzcode(up->tzhead.tzh_timecnt); - int_fast32_t typecnt = detzcode(up->tzhead.tzh_typecnt); - int_fast32_t charcnt = detzcode(up->tzhead.tzh_charcnt); - char const *p = up->buf + tzheadsize; - /* Although tzfile(5) currently requires typecnt to be nonzero, - support future formats that may allow zero typecnt - in files that have a TZ string and no transitions. */ - if (! (0 <= leapcnt && leapcnt < TZ_MAX_LEAPS - && 0 <= typecnt && typecnt < TZ_MAX_TYPES - && 0 <= timecnt && timecnt < TZ_MAX_TIMES - && 0 <= charcnt && charcnt < TZ_MAX_CHARS - && (ttisstdcnt == typecnt || ttisstdcnt == 0) - && (ttisutcnt == typecnt || ttisutcnt == 0))) - return EINVAL; - if (nread - < (tzheadsize /* struct tzhead */ - + timecnt * stored /* ats */ + char version = up->tzhead.tzh_version[0]; + bool skip_datablock = stored == 4 && version; + int_fast32_t datablock_size; + int_fast32_t ttisstdcnt = detzcode(up->tzhead.tzh_ttisstdcnt); + int_fast32_t ttisutcnt = detzcode(up->tzhead.tzh_ttisutcnt); + int_fast64_t prevtr = -1; + int_fast32_t prevcorr; + int_fast32_t leapcnt = detzcode(up->tzhead.tzh_leapcnt); + int_fast32_t timecnt = detzcode(up->tzhead.tzh_timecnt); + int_fast32_t typecnt = detzcode(up->tzhead.tzh_typecnt); + int_fast32_t charcnt = detzcode(up->tzhead.tzh_charcnt); + char const *p = up->buf + tzheadsize; + /* Although tzfile(5) currently requires typecnt to be nonzero, + support future formats that may allow zero typecnt + in files that have a TZ string and no transitions. */ + if (! (0 <= leapcnt && leapcnt < TZ_MAX_LEAPS + && 0 <= typecnt && typecnt < TZ_MAX_TYPES + && 0 <= timecnt && timecnt < TZ_MAX_TIMES + && 0 <= charcnt && charcnt < TZ_MAX_CHARS + && 0 <= ttisstdcnt && ttisstdcnt < TZ_MAX_TYPES + && 0 <= ttisutcnt && ttisutcnt < TZ_MAX_TYPES)) + return EINVAL; + datablock_size + = (timecnt * stored /* ats */ + timecnt /* types */ + typecnt * 6 /* ttinfos */ + charcnt /* chars */ + leapcnt * (stored + 4) /* lsinfos */ + ttisstdcnt /* ttisstds */ - + ttisutcnt)) /* ttisuts */ + + ttisutcnt); /* ttisuts */ + if (nread < tzheadsize + datablock_size) + return EINVAL; + if (skip_datablock) + p += datablock_size; + else { + if (! ((ttisstdcnt == typecnt || ttisstdcnt == 0) + && (ttisutcnt == typecnt || ttisutcnt == 0))) return EINVAL; + sp->leapcnt = leapcnt; sp->timecnt = timecnt; sp->typecnt = typecnt; @@ -578,13 +588,14 @@ tzloadbody(char const *name, struct state *sp, bool doextend, ttisp->tt_ttisut = *p++; } } - /* - ** If this is an old file, we're done. - */ - if (up->tzhead.tzh_version[0] == '\0') - break; - nread -= p - up->buf; - memmove(up->buf, p, nread); + } + + nread -= p - up->buf; + memmove(up->buf, p, nread); + + /* If this is an old file, we're done. */ + if (!version) + break; } if (doextend && nread > 2 && up->buf[0] == '\n' && up->buf[nread - 1] == '\n' && -- 2.31.1

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Extra transition type is generated by zic with -r specified
by Almaz Mingaleev Oct. 26, 2021

Oct. 26, 2021

I’ve tried to generate a TZif file with transitions up to 1 Jan 2100 using zic with -r and “-b fat”. However, an extra transition type is generated for many (all?) time zones. That type’s UTC offset is zero and it is used only for the last transition in the 64-bit section. What I did: mkdir /tmp/zic cd /tmp/zic git clone https://github.com/eggert/tz.git . make -C . zic make -C . NDATA= rearguard.zi mkdir data ./zic -b fat -r /@4102444800 -d ./data rearguard.zi Below is an investigation for Australia/Lord_Howe (I don’t think choice matters here). I couldn’t find a way to force zdump to print transitions for a given TZif file. Instead, please see human-readable dumps from the TZif from our internal tools immediately below and raw byte information at the bottom if you’d prefer to work with that. These are local time transition types for Australia/Lord_Howe: Types gmtOffset (seconds),isDst,ttisgmt,ttisstd,[gmtOffset ISO],[DST?] 38180,0,,,PT10H36M20S,STD 0,0,,,PT0S,STD <- this is odd 36000,0,,,PT10H,STD 41400,1,,,PT11H30M,DST 37800,0,,,PT10H30M,STD 39600,1,,,PT11H,DST Transitions: transition,type,[UTC time],[Type offset],[Type isDST] … 4063275000,5,2098-10-04T15:30:00Z,PT11H,DST 4078998000,4,2099-04-04T15:00:00Z,PT10H30M,STD 4094724600,5,2099-10-03T15:30:00Z,PT11H,DST 4102444800,1,2100-01-01T00:00:00Z,PT0S,STD <- this is odd So, after the upper bound specified in -r, the transitions say that GMT is used. As I’d expect, the 32-bit transitions are not affected when the upper bound in -r is after 2038. However, with -r /@1634833073 the 32-bit section also has 6 transition types and the last transition sets offset to 0. Is that a bug or is there a reason for such behaviour? Thanks, Almaz Byte manipulations: typecnt is 5 in 32-bit section: xxd -seek 36(4+1+15+4*4) -len 4 data/Australia/Lord_Howe 64-bit section starts at offset 674. timecnt is 0xF0(=240) in 64-bit section: xxd -seek 706(674 + 20 + 3 * 4) -len 4 data/Australia/Lord_Howe typecnt is 6 in 64-bit section: xxd -seek 710(706 + 4) -len 4 data/Australia/Lord_Howe So, 64-bit header has one extra transition type. Let’s check how it is used and what that transition is: 2638 = 674 + 44 + 240 * 8 xxd -seek 2638 -len 240 -c 1 data/Australia/Lord_Howe prints transition types: 00000b38: 05 . 00000b39: 04 . 00000b3a: 05 . 00000b3b: 04 . 00000b3c: 05 . 00000b3d: 01 . Transition type is changing from 4 to 5, but the last one is 1. xxd -seek 2878 -len 36 -c 6 data/Australia/Lord_Howe prints local time type records: 00000b3e: 0000 9524 0004 ...$.. 00000b44: 0000 0000 0000 ...... <- the last transition type 00000b4a: 0000 8ca0 0008 ...... 00000b50: 0000 a1b8 010d ...... 00000b56: 0000 93a8 0013 ...... 00000b5c: 0000 9ab0 0119 ...... Which means that 1st type’s offset is 0 and that the last rule for Lord Howe is actually GMT.

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[PROPOSED] Improve Palestine predictions for 2025 and later
by Paul Eggert Oct. 25, 2021

Oct. 25, 2021

* NEWS: Mention this. * asia (Palestine): Guess Fri>=23, not lastFri, for fallback transitions in the future. Fri>=23 is more consistent with past practice than lastFri. The first differing prediction is a fallback on 2025-10-24, not 2025-10-31. --- NEWS | 10 ++++++++++ asia | 2 +- 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/NEWS b/NEWS index a7aa269..d83e01c 100644 --- a/NEWS +++ b/NEWS @@ -1,5 +1,15 @@ News for the tz database +Unreleased, experimental changes + + Changes to future timestamps + + Predict Palestine fallbacks to be the first Friday on or after + October 23, not October's last Friday, to be more consistent with + past practice. The first differing prediction is a fallback on + 2025-10-24, not 2025-10-31. + + Release 2021e - 2021-10-21 18:41:00 -0700 Changes to future timestamps diff --git a/asia b/asia index dd228e5..6d6b1de 100644 --- a/asia +++ b/asia @@ -3445,7 +3445,7 @@ Rule Palestine 2019 only - Mar 29 0:00 1:00 S Rule Palestine 2019 only - Oct Sat>=24 0:00 0 - Rule Palestine 2020 max - Mar Sat>=24 0:00 1:00 S Rule Palestine 2020 only - Oct 24 1:00 0 - -Rule Palestine 2021 max - Oct lastFri 1:00 0 - +Rule Palestine 2021 max - Oct Fri>=23 1:00 0 - # Zone NAME STDOFF RULES FORMAT [UNTIL] Zone Asia/Gaza 2:17:52 - LMT 1900 Oct -- 2.31.1

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Wrong name of timezone
by Igor Melnyk Oct. 25, 2021

Oct. 25, 2021

Hello! There is *Europe**/Kiev* timezone related to Ukraine. But Ukraine has the Ukrainian language and *Kiev* is in russian language. The correct name of the capital city of Ukraine is *Kyiv.* It must be changed. I know that it's not easy to do that but you must have some way to do that. For example, rename *Europe/Kiev* to *Europe/Kyiv* and make *Europe/Kiev* to be a temporary alias or link to *Europe/Kyiv.* What do you think about it? Best regards, Igor Melnyk.

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Re: [tz] Palestine winter time
by Paul Eggert Oct. 22, 2021

Oct. 22, 2021

On 10/21/21 01:03, heba.hamad(a)mtit.gov.ps wrote: > Could you please confirm that Palestine winter time has been adopted in IANA time zone database Yes, tzdb release 2021e was published today with the updated Palestine winter time. The announcement is archived here: https://mm.icann.org/pipermail/tz-announce/2021-October/000069.html

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[tz-announce] 2021e release of tz code and data available
by Paul Eggert via tz-announce Oct. 22, 2021

Oct. 22, 2021

The 2021e release of the tz code and data is available. This release reflects the following changes: Changes to future timestamps Palestine will fall back 10-29 (not 10-30) at 01:00. (Thanks to P Chan and Heba Hemad.) Here are links to the release files: https://www.iana.org/time-zones/repository/releases/tzcode2021e.tar.gz https://www.iana.org/time-zones/repository/releases/tzdata2021e.tar.gz https://www.iana.org/time-zones/repository/releases/tzdb-2021e.tar.lz The following convenience links are also available, although they may point to the previous release until the relevant caches are refreshed: https://www.iana.org/time-zones/repository/tzcode-latest.tar.gz https://www.iana.org/time-zones/repository/tzdata-latest.tar.gz https://www.iana.org/time-zones/repository/tzdb-latest.tar.lz Links are also available via plain HTTP, and via FTP from ftp://ftp.iana.org/tz/releases with the same basenames as above. Each release file has a GPG signature, which can be retrieved by appending ".asc" to the above URLs. Copies of these signatures are appended to this message. This release corresponds to commit b102002e5300d94c369796d5b70bae22b5af720d dated 2021-10-21 18:41:00 -0700 and tagged '2021e' in the development GitHub repository at <https://github.com/eggert/tz>. Here are the SHA-512 checksums for the release files: 87b0335129ea41c5f42f687f548712e5da892baa8494cecf5d34851beceecf6ae52f22104696ed187713cf9e502570eb2041e277dfd3c043c11d0253bfde685a tzcode2021e.tar.gz c1e8d04e049157ed5d4af0868855bbd75517e3d7e1db9c41d5283ff260109de46b6fac6be94828201d093e163d868044ac2a9db2bf0aeab800e264d0c73a9119 tzdata2021e.tar.gz 8abd662f07a91eed5b77d03eaa3e9ef59ce08b4e3fc14f9857095c3d4f2039e8ac216fc985b0cf87a823eacad064197c8ecb76ba531a9fc700014d7f0057aba8 tzdb-2021e.tar.lz Here are the GPG digital signatures for the release files: -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEEfjeSqdis99YzvBWI7ZfpDmKqfjQFAmFyF3cACgkQ7ZfpDmKq fjQKRw//c5HpFCN0vcPUIC/OQKTF/SXFOANCpHWypc/vgTVXFAsVu0zIKWdBuXXI 0zQDpbTcTJ2FfI5Z1JGNzeKa2G4Wy71lwwPu2mGDt0WCCAqh/l15XvgVEAM96YLG WZRK+WLKIVWgZ67NA2xWAt9VLgtA643Cgym1DCpsr9jTDAhGSYq8D0XC5OQHtfw2 oyzv4InTW+0EI14FQcQ3VqImLwGSefeYPfMBRjrAspqrTLez78vW914IWNKcgEoC pKCkq9+14u0L+G5j5E+f27gbRtZ4hZnIn5uNgItomJmGObW6khn0Huf+G6U1BAal 2zLSAYMubr1kq/6dP62QUivi1W2S3YRZDh20YsKxn214HW5qK5LdQKYruBGKOFou 7oAe91W3UW0vSJuboXj0Dbdc3p8Oay97eJ/kRDVKJZ95/UOQtwrkQi2wCbm19eC8 kvHdejbIrOvdl+ZpvkHIggQGSOchyXUASeqnX/9zirOAX0N05insC/ybJLAwepFm FqpvcfwjrJKCotAjFEEex1uIT5kgQwIumvtxLef3bGQgYtF1yfWMD0NSJAR1iAU2 BzXuikOLPNbHWpC41ODgRxBVaQnMpliC0WGJ/HiVT78ukEkx0MpcxyfnxjEDD7fz F3GlJlj/bw5rvsPrFzbSjYyzXfrn0u1y8/vgehUmtSj1K7MmB6I= =CliF -----END PGP SIGNATURE----- -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEEfjeSqdis99YzvBWI7ZfpDmKqfjQFAmFyF3cACgkQ7ZfpDmKq fjSLPw/9EDTMMp0ySiPkYgXICy+hYq78xDOpF5IU34tcvmL2j3OZiM49X//CQzNF 7kLoEkYenpjJZ9QU8V0w+26UJF3js/R3a9gLU3ybPZ7+o+NOanQK68z5EvggWGfm 0yVCGbPhsKNoP/2Xtpv3gLiT6WoBvJF6k16mRQtiE7ngLJ3OUpaWaQAZ73F+sMTY I5F++cAdTvOTHw6M4ORmvp8OMg2df1KVXf2MINQZkx3OVxw+y6zaMwcKUJHz81eY KCDO6DJyoj48/WNDxfIiYVk2YoOVm9I3HiqgmrojmniJFLCq/PkWGqU61gmNCSRv 5vLjb9qnfWQG8E3E44pdH8aqZt7z7kYdcL89y5UnDBlJMmoh/cPigjfBmAot7Erw 5Mj8pp/a7tcvHKIoGZscIzjRnffYDHTD6rNwStVvTfKyGE7O6Fa63yUnndCudqdu 6nZCQNkELrn9ber4ieJR6d46LOVFvqlMhCzhknZRUBkbtU4ltwBze8RvrGGhdyJ3 s9YQtGpY1uEcNF4JWzqkE9sXtPnevFERUT1hZdQpJ2NM0mrVKAfdLhryvJyi+t30 fbMbyqmYRhPuyk7OUPbduTIXc4IIpSzAaeQRFwZqDGSOuOj+8JSk6EX9Kwel7ahp 2PIzzyffxL7m2kG9+iAKckRHz0nyvoYGHQl1gsah9qUVx2Q/JIo= =kEHz -----END PGP SIGNATURE----- -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEEfjeSqdis99YzvBWI7ZfpDmKqfjQFAmFyF3cACgkQ7ZfpDmKq fjSLPw/9EDTMMp0ySiPkYgXICy+hYq78xDOpF5IU34tcvmL2j3OZiM49X//CQzNF 7kLoEkYenpjJZ9QU8V0w+26UJF3js/R3a9gLU3ybPZ7+o+NOanQK68z5EvggWGfm 0yVCGbPhsKNoP/2Xtpv3gLiT6WoBvJF6k16mRQtiE7ngLJ3OUpaWaQAZ73F+sMTY I5F++cAdTvOTHw6M4ORmvp8OMg2df1KVXf2MINQZkx3OVxw+y6zaMwcKUJHz81eY KCDO6DJyoj48/WNDxfIiYVk2YoOVm9I3HiqgmrojmniJFLCq/PkWGqU61gmNCSRv 5vLjb9qnfWQG8E3E44pdH8aqZt7z7kYdcL89y5UnDBlJMmoh/cPigjfBmAot7Erw 5Mj8pp/a7tcvHKIoGZscIzjRnffYDHTD6rNwStVvTfKyGE7O6Fa63yUnndCudqdu 6nZCQNkELrn9ber4ieJR6d46LOVFvqlMhCzhknZRUBkbtU4ltwBze8RvrGGhdyJ3 s9YQtGpY1uEcNF4JWzqkE9sXtPnevFERUT1hZdQpJ2NM0mrVKAfdLhryvJyi+t30 fbMbyqmYRhPuyk7OUPbduTIXc4IIpSzAaeQRFwZqDGSOuOj+8JSk6EX9Kwel7ahp 2PIzzyffxL7m2kG9+iAKckRHz0nyvoYGHQl1gsah9qUVx2Q/JIo= =kEHz -----END PGP SIGNATURE----- PS. If your tzdata parser does not yet support negative DST offsets or times past 24:00, or if it insists on a 'pacificnew' file that is no longer present, this release's data entries can be turned into a rearguard-format tarball that should work even with these older parsers. This is intended to be a temporary transition aid for these parsers. To generate a rearguard-format tarball, obtain the full distribution as described above, and run the command 'make rearguard_tarballs' on a development host. Or you can run 'make rearguard.zi' to generate a single file that can be fed directly to a parser that works like 'zic'.

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Re: [tz] Palestine winter time
by Paul Eggert Oct. 21, 2021

Oct. 21, 2021

On 10/20/21 01:47, heba.hamad(a)mtit.gov.ps wrote: > winter time will begin in Palestine from Friday 10-29 ,01:00 AM by 60 minutes backwards. Thank you for letting us know. Attached is a proposed change to tzdb, installed into its development version <https://github.com/eggert/tz>. We plan to have a new tzdb release soon. This change implements this year's transition, and also guesses that winter time will begin on October's last Friday at 01:00 in 2022 and later years, to be consistent with 2021. If this guess is wrong, please let us know as far in advance as possible, because rule changes trickle out only slowly to cell phones and computers.

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The origin of time zone regions
by Arthur David Olson Oct. 21, 2021

Oct. 21, 2021

A middling-length story with a small point. In the seventies and eighties, I helped develop two-dimensional PAGE* image analysis software. Black and white images had a thousand or so spots; the positions of the spots and their size provided information on the characteristics and abundances of proteins in samples. Step one was to get the positions and sizes of spots in a single image. Step two was to compare two images, pairing up the spots. Some spots would only appear in one image and have no pairs; in other cases, two (or more) spots would appear in one image where only one appeared in the other; one spot would be paired with multiple spots. The final step was to consider groups of images. For this purpose, there were groups of spots where (to quote an article on the matter) “each spot in a group is paired with some other spot in the group and no spot in any group is paired with any spot in any other group.” In the mid-eighties, work started on the time zone database. And time zone regions ended up being defined as being places where all the clocks agreed. The small point: the nature of time zone regions has less to do with chronometry or geopolitics than it does with gel analysis. @dashdashado _ * https://www.sciencedirect.com/topics/neuroscience/two-dimensional-gel-elect…

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Re: [tz] Pre-1970 data
by Stijn “Adhemar” Vandamme Oct. 20, 2021

Oct. 20, 2021

The “should timezones be merged when they contain identical offsets from 1970 onwards” discussion has been going on for quite a while on the tz mailing list. Still, contributions that I find insightful are still being made. Stephen Colebourne recently made this observation: > The key observation is that the segregation between these two groups > > of IDs *did not exist* until around 2014. It was only in 2018 that the > > ISO country rule was removed. > This change was reflected in the documentation <theory.html> as recently as 20/21 February 2019 < https://github.com/eggert/tz/commit/5f48dee82bc111b21f3610893e3b788e37396bce > < https://github.com/eggert/tz/commit/6176aefe79e83ddb8f255849b85c149f34d46aba > And Stephen made this spot-on point of analysis: > FWIW, it is clear to me that there is an aspect of imposing a > > US-centric timezone system on other parts of the world. The recent > > tzdb approach of focussing entirely on timezone regions makes perfect > > sense for the US, where region boundaries do not follow state lines, > > and ordinary members of the public need to be aware of whether they > > are in US/Mountain or US/Central. This simply isn't the timezone model > > in many other parts of the world. In places like Europe and Asia, the > > timezone is driven primarily by the country you live in - an ordinary > > member of the public in Iceland is never going to associate with some > > abstract timezone region stretching down the Atlantic that is not > > named, not legally defined and is little more than a random outcome > > based on tzdb's choice of 1970. Even in somewhere like Norway, an > > ordinary member of the public will understand that although they > > follow CET, their timezone is actually driven by their Government in > > Oslo. The brilliance of the original rule - "ID as needed for > > post-1970 data, with at least one per ISO country" - was that it > > seamlessly handled *both* models of timezone in one unified set of > > IDs. Removal of the ISO country part has completely destabilised that > > balance. > If I may throw in my two-penny, it would pertain to the documentation of this policy. Presently, <theory.html> does mention - that timezones are zones whose clocks all agree about timestamps that occur after the 1970 POSIX Epoch; - that 1970 is indeed a somewhat-arbitrary cutoff, but that moving it earlier even by a decade or two would impose significant challenges, due to the wide variety of local practices before computer timekeeping became prevalent; - that pre-1970 clock transitions are recorded for location-based timezones, but that the database is not designed for and does not suffice for applications requiring accurate handling of all past times everywhere; - that the previous “at-least-one-timezone-per-country-with-officially-designated-ISO-3166-1-two-letter-country-code” rule is dropped for this imposed too high a maintenance burden; and - that some information outside the scope of the database (implied: pre-1970) is collected in a file backzone that is distributed along with the database proper, but that this file is less reliable and does not necessarily follow database guidelines. What astonishes me in this issue is that high-quality information is being removed from the database proper into backzone, without this being mentioned in the documentation <theory.html>. Granted, <theory.html> does not explicitly state an “at-least-attempt-to-get-monotonically-closer-to-the-truth-with-increasing-versions” policy, but one would think that’s implied in maintaining a (versioned) database, unless explicitly stated otherwise. The other way around (moving information from backzone to the database proper, e.g. when historical information is double-checked and confirmed to be in accordance with database guidelines) is totally acceptable without mentioning in the documentation <theory.html>. Indeed, even though I know that correcting pre-1970 data is not the priority of this project, I’ve seen some great sluthing of historical time zone offsets presented on the tz mailing list in the past, and I kinda assumed that the results of such research found its way to the database proper (or backzone when doubts remained). In my opinion, removing high-quality information — thereby having correct offsets changed into incorrect offsets in information systems that rely on the tz database and keep it up-to-date on the default settings (which disregard backzone) — should cease, and should preferably be undone where such damage has already occured. Seeing how much problems pursuing “fairness” under the new rules causes, perhaps it’s worth reinstating the previous “at-least-one-timezone-per-country-with-officially-designated-ISO-3166-1-two-letter-country-code” rule, either officially or unofficially. (And for what it’s worth, this comes from someone who generally tries to avoid relying on country lists such as ISO 3166-1, due to strong political belief in the desirability of independence or at least increased self-governance for several countries/regions currently lacking an officially-designated ISO 3166-1 two-letter country code, including Flanders, Wallonia, Scotland, Catalonia, Basque Country, Canary Islands, Tibet, and others.) But alternatively, if this project persists in its “removing-high-quality-information and merging-for-merging’s-sake” policy, then at the very least this should be mentioned clearly, unambiguously and conspicuously highlighted (bold, bigger font size, bright but fully saturated background colour, following an animated warning icon, the lot) in the documentation <theory.html>: PREVIOUSLY OR CURRENTLY CORRECT PRE-1970 OFFSET INFORMATION IS > INTENTIONALLY BEING CHANGED AND/OR MAY INTENTIONALLY BE CHANGED IN LATER > VERSIONS OF THE tz DATABASE INTO INCORRECT OFFSET INFORMATION for the > braindead reason of merging timezones for merging’s sake. > USERS MUST NOT RELY ON UNDISPUTEDLY AND UNCONTESTEDLY CORRECT AND VERIFIED > OFFSET INFORMATION REMAINING CORRECT in the database proper, except for > timezones that have post-1970 particularities which prevent them from being > merged with foreign timezones. (And even then — who knows what the > coordinator-maintainer will come up with next…) > Information systems that rely on tz for offset information, including for > pre-1970 datetimes-with-timezone-identifier, ought to pass this warning on > to their users. > — Adhemar

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