GNU bug report logs - #55635
`make-decoded-time' incorrectly sets DST to nil, it should be -1 (guess)

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From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: Eli Zaretskii <eliz <at> gnu.org>, 55635-done <at> debbugs.gnu.org, Maxim Nikulin <m.a.nikulin <at> gmail.com>
Subject: bug#55635: `make-decoded-time' incorrectly sets DST to nil, it should be -1 (guess)
Date: Sun, 29 May 2022 15:04:38 -0700

[Message part 1 (text/plain, inline)]

On 5/29/22 06:10, Lars Ingebrigtsen wrote:
> Paul Eggert <eggert <at> cs.ucla.edu> writes:
> 
>> With that in mind, here are three suggestions.
>>
>> 1. decoded-time-dst should return -1, instead of nil, when given a
>> 6-element list, since nil means standard time and -1 means DST is
>> unknown.
> 
> I think that sounds correct.

I looked into that, and since decoded-time-dst is defined by 
cl-defstruct it's not easy to change how it works. For now, I just 
documented the glitch; see the 3rd attached patch.

I also installed the 1st attached patch which mentions that Emacs's 
decoded dst flag differs from that of Common Lisp, and the 2nd attached 
patch which makes iso8601 parsing compatible with what we've discussed 
here by having it return -1 for unknown DST flags.


>> > 2. make-decoded-time should generate a six-element list unless given a
>> > DST or ZONE arg.
> 
> I don't think we should do this.

OK, I left that alone.

[0001-Doc-fix-for-dst-flag.patch (text/x-patch, attachment)]

[0002-ISO-8601-strings-sans-Z-don-t-specify-DST-flag.patch (text/x-patch, attachment)]

[0003-Document-decoded-time-string-issue-on-6-elt-args.patch (text/x-patch, attachment)]

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