[tz] Timezones Morocco 2013 incorrect

Patrice Scattolin patrice.scattolin at oracle.com
Thu Mar 7 18:30:10 UTC 2013

On 07/03/2013 1:33 AM, Paul Eggert wrote:
> On 03/06/2013 09:13 AM, Patrice Scattolin wrote:
>> Since we have no idea of emacs' algorithm
> We have the source code, so we can get an idea.
> The code can be found here:
> http://bzr.savannah.gnu.org/lh/emacs/trunk/annotate/head:/lisp/calendar/cal-islam.el
Ah yes, lisp! http://xkcd.com/297/

> Dershowitz and Reingold mention that there are other arithmetical
> approximations.  In particular, some Microsoft products
> use a variant approximation.  So it appears that no matter which
> approximation we'll use, we're bound to disagree with somebody's
> else's prediction.
The age and position of the moon are accurate enough (even with Meeus 
who is accurate enough for amateur planetarium software but notably not 
enough for more exacting tasks). It's the criteria upon when the moon 
crescent is actually observable that is up for debate. Since this relies 
most on the observer's skills, no matter who's approximation we rely 
upon we can certainly get it wrong by a day on some occasions.  
Apparently beginning of the Ramadan is a waiting game anyways 
so I doubt we can actually do better no matter algorithm.

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