[uf-discuss] Human and machine readable data format

[Toby A Inkster]

Scott Reynen wrote:

> I'm assuming by "different calendar," you mean non-Gregorian?  If so,
> what are the use cases for non-Gregorian dates in hCalendar?

It's not so much the case of wanting to encode non-Gregorian dates in  
hCalendar, but wanting to include non-Gregorian dates on the web page.

   <abbr class="dtstart" title="2008-07-14">11 Rajab 1429</abbr>

Is '2008-07-14' to be considered an appropriate expansion of the  
"abbreviation" '11 Rajab 1429'?

In case anyone is wondering whether non-Gregorian calendars are used  
in practice, the Islamic calendar (used in the example above) is the  
official calendar for Saudi Arabia, and used in religious contexts in  
many other countries; the Julian calendar is still used in religious  
contexts by Orthodox Christian churches, and frequently used by  
historians to refer to many older dates; the Chinese calendar is used  
for various religious and cultural reasons not just in China, but in  
some other Asian countries, but not for any official purposes.

I would cite specific pages that use these calendars, but I don't  
speak Arabic, Russian or Mandarin, so don't know the correct terms to  
Google for.

So there will be cases where people want to publish non-Gregorian  
dates, but for interoperability with iCalendar, they'll need to  
include a machine-readable Gregorian equivalent date. This is an  
example of where you're going to have very significant differences  
between the human and machine-readable representations of the same  
dates.

(It's also interesting to note that automatic translation from the  
Islamic calendar to Gregorian is impossible to perform reliably, as  
it is based on human observation of the movements of the sun and  
moon, not on the actual -- predictable -- movements of the sun and  
the moon. Thus the exact numbering of dates is not usually known very  
far in advance.)

-- 
Toby A Inkster
<mailto:mail at tobyinkster.co.uk>
<http://tobyinkster.co.uk>