[Tzdist-bis] Extend POSIX TZ to allow transition times outside 00-24 range, permanent DST
Paul Eggert <eggert@cs.ucla.edu> Mon, 03 June 2019 20:34 UTC
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From: Paul Eggert <eggert@cs.ucla.edu>
To: Time zone mailing list <tz@iana.org>
Cc: Extensions to Time Zone Data Distribution Service <tzdist-bis@ietf.org>
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Date: Mon, 03 Jun 2019 13:34:38 -0700
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Archived-At: <https://mailarchive.ietf.org/arch/msg/tzdist-bis/inhJS7rUytL77PeDjawsEl8vvFk>
Subject: [Tzdist-bis] Extend POSIX TZ to allow transition times outside 00-24 range, permanent DST
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I recently proposed extending the POSIX spec for TZ strings. Please see: http://austingroupbugs.net/view.php?id=1252 This proposal is a modest one, as it doesn't specify TZ strings like 'America/Los_Angeles'. Instead it merely specifies the strings generated by zic and stored into TZif files. This includes strings like '<-03>3<-02>,M3.5.0/-2,M10.5.0/-1' which use times of day outside the 00-24 range, and strings like 'EST5EDT,0/0,J365/25' that represent permanent daylight saving time. This extension to POSIX TZ strings has already been specified in Internet RFC 8536 section 3.3.1 <https://tools.ietf.org/html/rfc8536#page-13> and I think it's a good idea to backport the extension to POSIX itself, as this will bless the common practice of taking the last line of a TZif file and using it as a TZ string on small platforms that lack room to store the TZif files. Please feel free to comment at austingroupbugs.net.