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The names are, I think, the least problem--- we can just define a controlled
vocabulary. 
The biggest problem is that calendars such as the Jewish/Hebrew don't have
reversible transformations into Gregorian or Julian unless time and day of the
week are also specified--- from which one could determine if its before
sundown at the place (and, in fact, the same location may have two different
representations for two different people as there are sometimes multiple
customs that might be called upon to define sundown). 
Keeping to the Jewish/Hebrew calendar (and the Babylonian and other Lunisolar
calendars as well) we also can't resolve completely against our min/sec model. 
The Jewish hour is divided into 1080 units: 72 units per degree celestial
rotation or 360 * 72/ 24. Going back to Hebrew/Jewish now from a transformed
date, however, won't work since the Julian/Gergorian day ends at Midnight and
there is no way to determine the date. Its roughly based upon the stars
viewable from the location--- with good visibility-- 
http://www.jewishencyclopedia.com/view.jsp?artid=1166&letter=S
and so these is insufficient information in a date/time to go back.

On Mon, 8 Nov 2010 10:06:48 -0500, Denenberg, Ray wrote 
> From: Discussion of the Developing Date/Time Standards
[mailto:[log in to unmask]] On Behalf Of Simon Grant 
> Sent: Saturday, November 06, 2010 8:13 AM 
> To: [log in to unmask] 
> Subject: Re: [DATETIME] Extended Date/Time Format DRAFT specification for
review through December 6 
> "3. Miscellaneous / Calendar 
> It seems a no-brainer to define "julian" as an alternative to "gregorian",
though other calendars would presumably be more difficult, as they may have
different components. At least, in my limited understanding, Julian and
Gregorian calendars have the same components." 
>   
> I took my cue here from the draft VCard specification,
http://tools.ietf.org/html/draft-ietf-vcarddav-vcardrev-11#section-5.7, and
also the draft HTML5 spec (at least the WHATWG version if not WC) calendar
parameter (calscale), in which they define only the single value, 'gregorian'. 
>   
> My thinking is, I am hesitant to specify any values for calendars at all, as
I am unaware of any established vocabulary for calendar names (however, if
there is one, I would be interested in revisiting this issue). I am not
terribly reluctant to specify 'gregorian' because the vCard specification uses
that term, and even though that's a draft spec, if's a safe bet that it won't
change. I'm sure if's a safe bet that when Julian calendars are accomodated
the term 'julian' will be used. But there may also be good reasons why vCard
and the HTML people didn't want to include it now, perhaps because if they did
then the spec would need to detail the differences.  
>   
> Anyway this is open for discussion. 
>   
> --Ray 
>   
>   
>

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