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Re: XHTML 2.0 <datetime> element proposal

From: Lachlan Hunt <lhunt07@postoffice.csu.edu.au>
Date: Mon, 03 Nov 2003 00:46:01 +1100
Message-ID: <3FA50A99.7080609@postoffice.csu.edu.au>
To: www-html@w3.org

Hi,
  After researching this topic some more, I had a thought, that although 
the ISO 8601 date format is completely acceptable for most of the needs 
of writing dates and times in documents, and thus a datetime tag such as:
<datetime datetime="2003-11-03T00:45:00+10:00">3 November 2003, 
00:45</datetime>
would be fine, however, there are some limitations to this format.

  According to Calendopaedia[1], there a 5 calenders in widespread use 
around the world -- the Gregorian, Chinese, Hebrew, Persian and 
Islamic.  There are also other various calendars still used in some 
areas, such as the Julian.  As most of you would probably already know, 
some of these are lunar calendars and others are solar.  However, there 
are also Astronomical calendars that are calculated from the Earth's 
position relative to the stars (I think that's where the term 'Star 
Date' came from for all those Star Trek fans out there), and, yes, these 
calendars are in use in some astronomy areas, I've seen them.

  Most of these calendars mentioned above have differ greatly in the 
length of one year, and thus the ISO format cannot represent any of 
these accurately because it is based on the Gregorian calendar only.  
Not only this, but I do not believe that the ISO calendar allows for 
both CE and BCE (also known as AD and BC respectively) years.  eg.  How 
do you write the year 10BCE in ISO format?  please correct me if I'm 
wrong about this.

  IMO, creating a system in XML that can represent all these calendars 
is *out of the scope of XHTML*, and would require the creation of a new 
XML application, perhaps known as XDate (or XDateTime), which could then 
be integrated into XHTML, or any other XML document, using an 
appropriate namespace.

  This would be useful for any computer systems that require to 
represent dates in other calendars, such as astronomy systems based on 
'star Dates'.  It may, of course, be possible to write applications so 
that they automatically convert ISO 8601 and any other calendar, however 
this may be inconvenient and take valuable processing time, especially 
for real time applications that need to work and process data quickly.

  XDate would need to provide that ability to represent, at least, most 
of the above mentioned calendars, if not more.  Ideally, it would be 
able to represent every calendar known to man, however, the complexity 
of this may be too huge.  As a starting guide, XDate could use the work 
already done by Sun when creating the java.util.Calendar[2] and 
java.util.GregorianCalendar[3] java classes which provide means to 
represent the many date and time properties such as era (AD or CE, and 
BC or BCE), timezone, DST offset, am/pm/24hr, etc.  These two java 
classes were the inspiration behind my initial datetime post[4] to this 
list.

  As a final note, IMO, this would fully support i18n since it's goal 
would be to represent the world's calendars in a single structured 
format, portable across virtually any computer system these days.

[1] http://www.geocities.com/calendopaedia/
[2] http://java.sun.com/j2se/1.4.2/docs/api/java/util/Calendar.html
[3] http://java.sun.com/j2se/1.4.2/docs/api/java/util/GregorianCalendar.html
[4] http://lists.w3.org/Archives/Public/www-html/2003Oct/0083.html

CYA
...Lachy
Received on Sunday, 2 November 2003 08:46:02 UTC

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