From: Paul Eggert <eggert@CS.UCLA.EDU>
Cc: bug-gnu-emacs@gnu.org
Subject: cal-persia.el disagrees with Iranian calendar in A.D. 2025
Date: Wed, 30 Mar 2005 12:29:33 -0500 [thread overview]
Message-ID: <87sm2d82ki.fsf@penguin.cs.ucla.edu> (raw)
A time-zone database user reported a bug for the year 2025 in Iran.
This appears to be due to a disagreement between GNU Emacs's
cal-persia.el and the user's (German) source for the Persian calendar.
The problem occurs both with Emacs 21.4 and CVS head.
I enclose the user's email below. I confirmed that
(calendar-gregorian-from-absolute
(calendar-absolute-from-persian '(1 1 1404)))
returns (3 20 2025), so it does appear that cal-persia disagrees with
his source, which says that 1 Farvardin 1404 corresponds to 21 March
2025. I don't know whether this should be a code fix or an
enhancement (cal-iran.el, say?).
> From: Oscar van Vlijmen <ovv@hetnet.nl>
> Subject: Iran calculated DST dates
> Date: Wed, 30 Mar 2005 14:38:46 +0200
>
> I checked the DST on/off dates for Iran.
> It appears that the dates were calculated with the arithmetic 'Persian'
> calendar in mind. Since 1925 an astronomical calendar is in use, so I read.
> There is one day difference between these two calendar systems in the
> Gregorian year 2025, so there is one error in the list of DST rules for Iran
> if indeed the astronomical calendar system is used.
>
> The astronomical Iranian calendar has 1 Farvardin 1404 on 21 March 2025
> Gregorian, so DST on is per 22 March 2025 0:00, and 30 Shahrivar 1404 is on
> 21 September 2025 Gregorian, so DST off is per 22 September 2025 Gregorian.
>
> The vernal equinox in 2025 Gregorian is at around 09:01 UTC on March 20, so
> around 12:27 Tehran 'solar' time. This is past 12:00, hence 1 Farvardin is
> on March 21.
>
> A long article about the Iranian calendar (in German):
> Iranische Zeitrechnungen, Nikolaus A. Bär, 2004.
> See the chapter "Der neuiranische Kalender", with a French translation of
> the 1925 law.
> http://www.nabkal.de/irankal.html
>
> I checked the Iranian calendar dates with the Java application by
> Reingold/Dershowitz, version 2.1.
> http://emr.cs.iit.edu/home/reingold/calendar-book/Calendrica.html
> And the mentioned vernal equinox date/time with 2 different astronomical
> programs.
>
> Oscar van Vlijmen
> 2005-03-30
>
next reply other threads:[~2005-03-30 17:29 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <eggert@CS.UCLA.EDU>
2005-03-30 17:29 ` Paul Eggert [this message]
2005-03-30 18:25 ` cal-persia.el disagrees with Iranian calendar in A.D. 2025 Ed Reingold
[not found] <200503302100.j2UL0wFG007410@emr.cs.iit.edu>
2005-03-31 7:18 ` Paul Eggert
2005-03-31 14:39 ` Ed Reingold
2005-04-05 16:14 ` Roozbeh Pournader
2005-04-05 22:02 ` Paul Eggert
2005-04-06 13:12 ` Roozbeh Pournader
2005-04-06 16:30 ` Ed Reingold
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