bug#69894: 29.1; Icalendar export conflict with calendar iso date

[Erwan Hingant via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Sorry I cannot help much because I am not an expert in 
regexp.... I just find a patch which work for me. The 0? is not in 
the match, the function assume a good structure of the diary file 
so 2024 099 03 will match 2024 99 3 if I am right? What I am 
concern is considering - instead of space likewise the default ISO 
format used .

E.

Paul Eggert <eggert@cs.ucla.edu> writes:

> On 3/28/24 03:53, Eli Zaretskii wrote:
>>> diff -u --label 
>>> /usr/local/share/emacs/29.1/lisp/calendar/icalendar.el.gz 
>>> --label /tmp/icalendar.el /tmp/jka-commHr8dl /tmp/icalendar.el
>>> --- /usr/local/share/emacs/29.1/lisp/calendar/icalendar.el.gz
>>> +++ /tmp/icalendar.el
>>> @@ -894,8 +894,8 @@
>>>       (save-match-data
>>>         (cond ( ;; iso-style numeric date
>>>                (string-match (concat "\\s-*"
>>> -                                   "\\([0-9]\\{4\\}\\)[ 
>>> \t/]\\s-*"
>>> -                                   "0?\\([1-9][0-9]?\\)[ 
>>> \t/]\\s-*"
>>> +                                   "\\([0-9]\\{4\\}\\)[ 
>>> \t/-]\\s-*"
>>> +                                   "0?\\([1-9][0-9]?\\)[ 
>>> \t/-]\\s-*"
>>>                                      "0?\\([1-9][0-9]?\\)")
>>>                              datestring)
>>>                (setq year (read (substring datestring 
>>>                (match-beginning 1)
>>>
>>> Diff finished.  Tue Mar 19 02:40:06 2024
>>>
>>> Is it a correct solution to proposed?
>> Paul, WDYT about the proposed change?
>
> I'm no expert on diary files. Certainly the "-" is ISO format 
> (space and tab are not).
>
> By the way, those two instances of 0?\\([1-9][0-9]?\\) both look 
> bogus to me, as they
> match strings like 099 that are implausible month or 
> day-of-month numbers.