GNU bug report logs - #78096
31.0.50; calendar-iso-to-absolute and %W time string format are inconsistent

Previous Next

To reply to this bug, email your comments to 78096 AT debbugs.gnu.org.

Toggle the display of automated, internal messages from the tracker.

Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Ihor Radchenko <yantar92 <at> posteo.net>
To: bug-gnu-emacs <at> gnu.org
Subject: 31.0.50; calendar-iso-to-absolute and %W time string format are
 inconsistent
Date: Sun, 27 Apr 2025 15:28:43 +0000

Hi,

This bug was originally reported in
https://orgmode.org/list/174544167676.8.6104466990232889732.690779499 <at> publik.slmail.me

Consider the following:

(calendar-gregorian-from-absolute
  ;; First day of the second week of 2025
  (calendar-iso-to-absolute (list 2 1 2025))) ; => 2025-01-06

Now, let's try to format the same date using `format-time-string'

(format-time-string
  "%Y-%m-%d W%W"
  (encode-time (parse-time-string "2025-01-06 00:00")))
;; => 2025-01-06 W01

As you can see, week numbering is off by 1 between %W and
`calendar-iso-to-absolute', which is unexpected.

I believe that it is a bug.

In GNU Emacs 31.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
 3.24.42, cairo version 1.18.2) of 2025-04-22 built on localhost
Repository revision: a9ace435a341918eae3e01f2941f5bbca04d7795
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12101014
System Description: Gentoo Linux

-- 
Ihor Radchenko // yantar92,
Org mode maintainer,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
or support my work at <https://liberapay.com/yantar92>

Message #8 received at 78096 <at> debbugs.gnu.org (full text, mbox):

From: Stephen Berman <stephen.berman <at> gmx.net>
To: Ihor Radchenko <yantar92 <at> posteo.net>
Cc: 78096 <at> debbugs.gnu.org
Subject: Re: bug#78096: 31.0.50; calendar-iso-to-absolute and %W time string
 format are inconsistent
Date: Sun, 27 Apr 2025 23:05:06 +0200

On Sun, 27 Apr 2025 15:28:43 +0000 Ihor Radchenko <yantar92 <at> posteo.net> wrote:

> Hi,
>
> This bug was originally reported in
> https://orgmode.org/list/174544167676.8.6104466990232889732.690779499 <at> publik.slmail.me
>
> Consider the following:
>
> (calendar-gregorian-from-absolute
>   ;; First day of the second week of 2025
>   (calendar-iso-to-absolute (list 2 1 2025))) ; => 2025-01-06
>
> Now, let's try to format the same date using `format-time-string'
>
> (format-time-string
>   "%Y-%m-%d W%W"
>   (encode-time (parse-time-string "2025-01-06 00:00")))
> ;; => 2025-01-06 W01
>
> As you can see, week numbering is off by 1 between %W and
> `calendar-iso-to-absolute', which is unexpected.
>
> I believe that it is a bug.

The doc string of `format-time-string' says:

%U is the week number starting on Sunday, %W starting on Monday,
 %V the week number according to ISO 8601.

(format-time-string
  "%Y-%m-%d W%V"
  (encode-time (parse-time-string "2025-01-06 00:00")))
=> "2025-01-06 W02"

Maybe just starting the week on Monday does not guarantee that the
result is an ISO commercial date?

Steve Berman

Message #11 received at 78096 <at> debbugs.gnu.org (full text, mbox):

From: Ihor Radchenko <yantar92 <at> posteo.net>
To: Stephen Berman <stephen.berman <at> gmx.net>
Cc: 78096 <at> debbugs.gnu.org
Subject: Re: bug#78096: 31.0.50; calendar-iso-to-absolute and %W time string
 format are inconsistent
Date: Mon, 28 Apr 2025 16:05:43 +0000

Stephen Berman <stephen.berman <at> gmx.net> writes:

> The doc string of `format-time-string' says:
>
> %U is the week number starting on Sunday, %W starting on Monday,
>  %V the week number according to ISO 8601.
>
> (format-time-string
>   "%Y-%m-%d W%V"
>   (encode-time (parse-time-string "2025-01-06 00:00")))
> => "2025-01-06 W02"

That indeed explains it - %W and %V are apparently not the same and
`calendar-iso-to-absolute' is closer to %V.

> Maybe just starting the week on Monday does not guarantee that the
> result is an ISO commercial date?

Unless you see some error I am not seeing here, this is probably not a
bug, but my misunderstanding.

-- 
Ihor Radchenko // yantar92,
Org mode maintainer,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
or support my work at <https://liberapay.com/yantar92>

Message #14 received at 78096 <at> debbugs.gnu.org (full text, mbox):

From: Andreas Schwab <schwab <at> linux-m68k.org>
To: Ihor Radchenko <yantar92 <at> posteo.net>
Cc: Stephen Berman <stephen.berman <at> gmx.net>, 78096 <at> debbugs.gnu.org
Subject: Re: bug#78096: 31.0.50; calendar-iso-to-absolute and %W time string
 format are inconsistent
Date: Mon, 28 Apr 2025 18:43:18 +0200

On Apr 28 2025, Ihor Radchenko wrote:

> Stephen Berman <stephen.berman <at> gmx.net> writes:
>
>> The doc string of `format-time-string' says:
>>
>> %U is the week number starting on Sunday, %W starting on Monday,
>>  %V the week number according to ISO 8601.
>>
>> (format-time-string
>>   "%Y-%m-%d W%V"
>>   (encode-time (parse-time-string "2025-01-06 00:00")))
>> => "2025-01-06 W02"
>
> That indeed explains it - %W and %V are apparently not the same and
> `calendar-iso-to-absolute' is closer to %V.

The difference is that %V is always the same for the whole week, whereas
%V and %W roll over on 01-01 (and use 0 for a partial first week).

$ for y in $(seq 2020 2025); do date -d "$y-01-01" +"%a %U %V %W"; done
Wed 00 01 00
Fri 00 53 00
Sat 00 52 00
Sun 01 52 00
Mon 00 01 01
Wed 00 01 00

-- 
Andreas Schwab, schwab <at> linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
"And now for something completely different."

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.