-- Gwyn Ciesla she/her/hers ------------------------------------------------ in your fear, seek only peace in your fear, seek only love -d. bowie Sent with Proton Mail secure email. On Wednesday, October 28th, 2026 at 3:47 PM, Peter Robinson <[email protected]> wrote: > On Wed, 28 Oct 2026 at 16:47, Aoife Moloney via devel-announce > <[email protected]> wrote: > > > > Wiki - https://fedoraproject.org/wiki/Changes/TzdataZicSlimFormat > > Discourse Poll - > > https://discussion.fedoraproject.org/t/f46-change-proposal-tzdatazicslimformat-system-wide/206308 > > > > This is a proposed Change for Fedora Linux. > > This document represents a proposed Change. As part of the Changes > > process, proposals are publicly announced in order to receive > > community feedback. This proposal will only be implemented if approved > > by the Fedora Engineering Steering Committee. > > > > > > == Summary == > > tzdata will use the default ‘slim’ data format for generating zoneinfo > > files rather than the previous 'fat’ data format. > > > > == Owner == > > > > * Name: [[User:pfrankli| Patsy Griffin]] > > > > * Email: [email protected] > > > > > > == Detailed Description == > > > > In 2019, the upstream tzdata project added the -b option to zic. > > The -b option supports a way to control data bloat and to test for > > year-2038 bugs in software that reads TZif files. > > 'zic -b fat' generates the traditional larger output files. 'zic -b > > slim' generates smaller output. > > > > In Fedora, tzdata currently uses the 'zic -b fat' format to generate > > zoneinfo files for compatibility with older software. > > > > The 'fat' and 'slim' files represent the same set of timestamps and > > use the same TZif > > format as documented in tzfile(5). > > > > The fat format tries to work around bugs or incompatibilities in > > older software. Specifically, software that mishandles 64-bit TZif data > > or uses obsolete TZ strings like EET-2EEST that lack DST rules. > > Slim format is more efficient and does not work around 64-bit bugs > > or obsolete TZ strings. > > > > Since 2020, the upstream project has been generating 'slim' format > > by default. > > > > This change request proposes transitioning to the default 'slim' > > format to reduce file size and provide advance warning of 2038 bugs in > > software that reads TZif files. > > > > == Feedback == > > > > I discussed this change with libstdc++. They do not think this change > > will impact them. > > Similarly, Java does not use the binary files and therefore does not > > expect to be impacted. > > I discussed this change with the pytz package maintainer. They > > observed some test failures but felt they could be handled with some > > code changes. > > It's also worth noting that pyrz is also deprecated in upstream python > for some time (3.9 if memory serves) and the new upstream way is > zoneinfo and there's already other issues with pytz. Absolutely. We I've been meaning to work on a pytz deprecation plan for some time; I'll step that effort up. -Signed, pytz maintainer. > > > == Benefit to Fedora == > > > > Use of zic's default slim file format will control data bloat and > > reduce zoneinfo file sizes. > > > > == Scope == > > * Proposal owners: > > This is a simple change for tzdata. We simply need to remove the > > command line option that forces zic to use the fat data format. > > > > * Other developers: > > Currently, we are aware that pytz may need some code changes. Having > > discussed this with the package owner, it is assumed to be a small > > amount of work. > > > > We don't know if other packages will be impacted. > > > > * Release engineering: No release engineering changes are required. > > > > * Policies and guidelines: N/A (not needed for this Change) > > > > * Trademark approval: N/A (not needed for this Change) > > > > * Alignment with the Fedora Strategy: > > > > > > == Upgrade/compatibility impact == > > > > No upgrade compatibility impact expected. > > > > == Early Testing (Optional) == > > > > Do you require 'QA Blueprint' support? N > > > > == How To Test == > > > > Create two copies of the zoneinfo using both zic -b fat and the > > default zic output. > > Use zdump to dump some zones from each version of zoneino, > > America/New_York for example. > > Compare the zone information for each version. The time zone > > information should be the same. > > NOTE: The 'fat' format may contain some extraneous information. > > > > == User Experience == > > > > Data files created by zic will now be considerably smaller. > > > > == Dependencies == > > > > > > == Contingency Plan == > > > > * Contingency mechanism: If this change results in unforeseen issues > > we can remove the proposal and leave tzdata as is until the unforeseen > > issues are resolved. > > > > * Contingency deadline: Beta freeze > > > > * Blocks release? This change should not block the release. > > > > == Documentation == > > > > The upstream tzdata NEWS file contains several entries relating to the > > zic 'slim' and 'fat' formats. > > > > == Release Notes == > > > > > > > > -- > > Aoife Moloney > > > > Fedora Operations Architect > > > > Fedora Project > > > > Matrix: @amoloney:fedora.im > > > > IRC: amoloney > > > > -- > > _______________________________________________ > > devel-announce mailing list -- [email protected] > > To unsubscribe send an email to [email protected] > > Fedora Code of Conduct: > > https://docs.fedoraproject.org/en-US/project/code-of-conduct/ > > List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines > > List Archives: > > https://lists.fedoraproject.org/archives/list/[email protected] > > Do not reply to spam, report it: > > https://forge.fedoraproject.org/infra/tickets/issues/new > -- > _______________________________________________ > devel mailing list -- [email protected] > To unsubscribe send an email to [email protected] > Fedora Code of Conduct: > https://docs.fedoraproject.org/en-US/project/code-of-conduct/ > List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines > List Archives: > https://lists.fedoraproject.org/archives/list/[email protected] > Do not reply to spam, report it: > https://forge.fedoraproject.org/infra/tickets/issues/new >
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