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

[Eli Zaretskii <eliz@gnu.org>]

> Date: Tue, 19 Mar 2024 02:56:57 +0100
> From:  RwN via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> 
> Dear All,
> 
> In a diary file, with a simple entry entry "2024-03-19 10:00 Appointment", icalendar-export-file process to an error: "Could not parse date". The entry is provided by the default value of calendar-iso-date-display-form.
> 
> I solve the problem with the following patch mathchin '-' has a separator in the function icalendar--datestring-to-isodate :
> 
> 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?