cal-persia.el disagrees with Iranian calendar in A.D. 2025
reingold at emr.cs.iit.edu
Thu Mar 31 14:39:38 UTC 2005
> It mentions the March 20, 2025 discrepancy, and it has some
> interesting and not-altogether-positive things to say about the method
> used in GNU Emacs. I hadn't realized how controversial this area is.
Had I realized how controversial it was, I would not have included it in
Emacs, I only learned that is 1998, long after the code was released.
Still, it is not a bad approximation, but it should be labeled as such.
> Thanks for clarifying this. Would it be appropriate to make the
> following change to the GNU Emacs user documentation, if only to help
> forestall future bug reports in this area?
Your change (below) is fine.
> 2005-03-31 Paul Eggert <eggert at cs.ucla.edu>
> * calendar.texi (Calendar Systems): Mention that the Persian
> calendar implemented is the arithmetical calendar of Birashk.
> --- calendar.texi.~1.33.~ 2005-03-28 16:30:06 -0500
> +++ calendar.texi 2005-03-31 01:46:45 -0500
> @@ -691,6 +691,12 @@ Their calendar consists of twelve months
> days, the next five have 30 days, and the last has 29 in ordinary years
> and 30 in leap years. Leap years occur in a complicated pattern every
> four or five years.
> +The calendar implemented here is the arithmetical Persian calendar
> +championed by Birashk, based on a 2,820-year cycle. It differs from
> +the astronomical Persian calendar, which is based on astronomical
> +events. As of this writing the first future discrepancy is projected
> +to occur on March 20, 2025. It is currently not clear what the
> +official calendar of Iran will be that far into the future.
> @cindex Chinese calendar
> The Chinese calendar is a complicated system of lunar months arranged
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