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Re: [whatwg] <time>

From: Robert J Burns <rob@robburns.com>
Date: Fri, 13 Mar 2009 04:02:58 -0500
Cc: Geoffrey Sneddon <foolistbar@googlemail.com>, David Singer <singer@apple.com>, Charles McCathieNevile <chaals@opera.com>, Toby A Inkster <mail@tobyinkster.co.uk>, whatwg@lists.whatwg.org, "public-html@w3.org" <public-html@w3.org>
Message-Id: <98A9EBCC-EB26-40F0-BCAA-9C7B0CD54C80@robburns.com>
To: Julian Reschke <julian.reschke@gmx.de>
Hi Julian,

On Mar 13, 2009, at 3:10 AM, Julian Reschke wrote:

> Robert J Burns wrote:
>> ...
>> Let us keep in mind that the HTML5 draft does not reference ISO  
>> 8601. It also already reaches way beyond ISO 8601 and claims to  
>> handle dates all the way back to 0000-01-01 whereas ISO 8601 only  
>> handles dates between 1582 and 9999. So HTML5 already takes on the  
>> task of specifying dates ...
>
> <http://en.wikipedia.org/wiki/ISO_8601#Years>:
>
> "The standard permits expansion to, for example, represent years  
> before 1582 or after 9999, but only by prior agreement between the  
> sender and the receiver."

Yes. in our case HTML5 would have to provide additional norms to  
define how to express those dates outside the ISO 8601 defined range  
(it isn't provided by ISO 8601 itself but merely suggests ways of  
expanding itself). That was precisely what I have been referring to  
repeatedly. So agreement between sender and receiver in this context  
implies additional norms to identify what the numbers mean when  
greater than 9999 and less than 1582. Earlier I had suggested adding a  
norm where delimiting hyphens are required to signify years greater  
than 9999: an additional norm necessary when allowing dates beyond the  
year 9999 (an alternative, for example, is to prohibit ordinal dates).  
I have also suggested that non-positive years should represent the  
value YYYY -1 to provide the additional criterion agreement to fill-in  
the missing gaps of ISO 8601 (so 0000 signifies -1 or 1 BC in the  
proleptic Gregorian calendar; an alternative would be to deviate from  
more common approaches without a year zero and include a year zero).

If ISO 8601 thought it had provided a complete normative specification  
for such dates it wouldn't need any further agreement between sender  
and receiver. So my original point stands. With ISO 8601 alone we only  
get Gregorian dates between 1582 and 9999. We would need other norms/ 
agreements/criteria to either come from this WG or to make room in  
HTML semantics for other specifications to fill in the gaps.

> We aren't the subject matter experts on calendars and date formats,  
> so why do we pretend we are?

So again, if we aren't experts on calendars and date formats then we  
also shouldn't presume we can provide the additional criteria  
agreements to expand ISO 8601 beyond the 1582 to 9999 dates. I'm not  
saying we cannot, but if we think about expanding ISO 8601 in that  
way, we might also consider enhancing it (or developing a variant) to  
support non-Gregorian dates. To me it is more troublesome to take up a  
controversial issue like the year zero in a proleptic Gregorian  
calendar than it is to support other calendars that either don't have  
that issue or have already addressed it in clearer ways (e.g., Julian,  
Hebrew, Buddhist, Julian Date, etc.). In other words we have to step  
in and claim to be more expert to settle the zero year issue than to  
step in and allow alternative calendars to be expressed in an ISO 8601  
like format (keep in mind several of these calendars are actually used  
as civil calendars in everyday business). Particularly if we only  
support the year zero itself and not BC years (as in the current  
draft), it seems completely ill-advised to take a stand on year zero  
(adding only one more year of support), while leaving out all the BC  
years.

Take care,
Rob
Received on Friday, 13 March 2009 09:04:30 UTC

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