W3C home > Mailing lists > Public > www-rdf-calendar@w3.org > December 2002

Re: ical schema based on 1 test case: mtg.ics

From: Charles McCathieNevile <charles@w3.org>
Date: Sat, 21 Dec 2002 00:28:31 -0500 (EST)
To: Dan Connolly <connolly@w3.org>
cc: <www-rdf-calendar@w3.org>
Message-ID: <Pine.LNX.4.30.0212202320020.11312-100000@tux.w3.org>

On 20 Dec 2002, Dan Connolly wrote:

>
>Following from our discussion today about the new workspace
>  http://www.w3.org/2002/12/cal/
[snip]
>Some design choices I'd like confirmation on...
>maybe these belong in the schema or in some
>other documentation...
[snip]
>calscale: previously, I treated GREGORIAN as a symbol
>(i.e. a URI) rather than a string. I backed
>that out because I don't think calscale is
>worth bothering with. I've never seen anything
>other than GREGORIAN, and the semantics
>of anything else isn't even specified by
>RFC 2445.

I am more and more coming across the situation where I want to know when
ramadan occurs, because it is equivalent to christmas in the US or Autralia
as a time when a whole lot of people are relatively inactive. I suspect
knowing Jewish holidays would be helpful to a number of people as well.
Although it is possible to just collect a comparison table that says "Ramadan
falls on this date and that date" it would be cleaner design to swap the
calendar as desired. (It would also be possible for a few well-known
characters to rely on well-known names - it is not architecturally elegant,
but for many applications it works sufficiently well).

Other use cases I have come across for non-Gregorian calendaring, or for
wanting to find the correspondences:

Planning according to menstrual cycle. This is something that real people do.
Often these will follow a lunar calendar, in which case an islamic calendar
works, or they will be regulated on a strict cycle of 28 days. (Without a
regular cycle it is rare to plan as if there is one, of course). This is the
strongest case I can think of for semantic richness in calendar descriptions.

Historical dating. The Gregorian calendar was adopted at different times in
different places. The last major country I know of to adopt it was China, in
1949. The USSR adopted it as a result of the bolshevik revolutio, the UK and
its then American colonies adopted it in the mid 18th century, long after
much of Europe. So comparing dates it is important to know what the calendar
in question is. (Although this problem was the one that motivated the
adoption of the Gregorian Calendar it isn't actually very strong, because
there is a relatively small need for precise date comparison.)

Astrology. People do this. Being able to look up the ephemerides in your
normal calendar is going to be the thing that makes that calendar valuable to
a number of people. (It would once have been important to navigators too,
but GPS probably means there isn't a significant number of users in that
group now).

Finding Easter. For non-orthodox churches (which is my own use case, and
therefore the one I am most familiar with) I believe this can be readily
determined with only a lunar calendar, a solar calendar, and a jewish
calendar (I need to know the first full moon after the equinox, and then
whether or not pasoch falls on that date). Aside from the planning involved
for christian folks there are a lot of secular events that take advantage of
what (in Australia and Europe) is a major holiday

Cheers

Chaals
Received on Saturday, 21 December 2002 00:28:34 GMT

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