Re: XML Timezones (fwd)

This is a difficult problem, and I wouldn't look for a quick-fix solution.

I recently had occasion to update an old Internet Draft by Chris Newman 
that profiled ISO8601 date/time formats [1] for use in IETF protocols.  The 
original draft (now long expired) included a considerable amount of 
material on timezones and their use for indicating schedule events (while 
what we actually wanted from this draft was a simple format for expressing 
timestamps).

As part of this exercise, Chris passed me a copy of his voluminous 
correspondence on the previous draft;  it was interesting to note that the 
vast majority of this correspondence was about the matter of timezones and 
their relation to scheduled events.  I got the impression that a complete 
solution is not really feasible because it would attempt to codify 
localized social behaviour, past present and future, in a global protocol.

I haven't noticed anything about specifying time-offset details separately 
from timezone identification -- that seems like a reasonable idea, but I 
tend to think that it might as well be specified as two distinct values 
(i.e. separate XML elements or RDF properties).

#g
--

[1] http://search.ietf.org/internet-drafts/draft-ietf-impp-datetime-05.txt


At 11:45 AM 12/23/01 -0500, Dan Brickley wrote:

>forwarded from the xmlschema-dev list...
>
>         http://lists.w3.org/Archives/Public/xmlschema-dev/
>         http://lists.w3.org/Archives/Public/xmlschema-dev/2001Dec/0233.html
>
>Can anyone advise? (crossposting between these two lists seems a
>reasonable thing to do, btw, if anyone has an answer!).
>
>cheers,
>
>Dan
>
>ps. has anyone tried to use DAML+OIL to define membership rules for
>classes of repeating events? see recent W3C Note(s)
>http://www.w3.org/TR/daml+oil-reference and nearby...
>
>---------- Forwarded message ----------
>Date: Sun, 23 Dec 2001 16:32:43 +0000 (GMT)
>From: s.livingstone@btinternet.com
>To: xmlschema-dev@w3.org
>Subject: XML Timezones
>Resent-Date: Sun, 23 Dec 2001 11:33:11 -0500 (EST)
>Resent-From: xmlschema-dev@w3.org
>
>I am writing a Windows Scheduling Service in C# that will use data in XML
>format to determine Scheduling information. This same file will be
>replicated globally and hence will be subject to timezone changes and
>daylight saving time.
>
>[my timezone values are just examples - they may not be correct!!]
>
>I was originally using the XSD dateTime data type to determine the date and
>time to perform a task, but this is limited when applied globally, because
>the offset (timezone) is based on local time and as soon as you replicate to
>some other timezone, the local time changes and so your scheduling
>information goes nuts.
>
>An example...
>
>We have a Scheduled item that is to be done on July 16th, 2002 at 2PM
>Scottish time.
>This is simple to express as July 16th, 2002 at 2PM GMT (summer has no
>daylight saving time).
>According to the XML Schema stanard
>(http://www.w3.org/TR/xmlschema-2/#dateTime) which uses the format
>"CCYY:MM:DDTHH:MMZ"
>this could be written as :
>"2002:07:16T14:00Z"
>
>However, this standard format doesn't work too great because in the winter
>the local time in Scotland changes to 1 hour less than UTC and so the
>scheduled time should change to "2002:07:16T13:00Z" or 1PM GMT, but how do
>you know this from the above fomat? Sure, it tells you the date, so you can
>work out whether Daylight Saving Time applies, but you don't know what
>timezone it refers to - it is a bad mistake to assume the local timezone,
>because if i moved the Schedule information to Santiago, Chile and we
>assumed the local settings to determine the offset then on that date the UTC
>time would be "2002:07:16T08:00Z" - because here we are 8 hours behind GMT
>on that date.
>
>There needs to be some way of stating the target timezone so that the
>correct Daylight settings relative to UTC can be resolved. Something like
>this...
>
>"CCYY:MM:DDTHH:MM:SSZGXXXX"
>
>where at the end, GXXXX specifies the locale identifier of the originally
>scheduled time.
>
>Does that make any sense?? Has there been talk of this before...
>
>I never really thought much about it until i had to use it in my app!!
>
>Cheers,
>Steven
>Author "XML Application Development with MSXML 4.0"
>www.deltabis.com

------------
Graham Klyne
GK@NineByNine.org

Received on Friday, 28 December 2001 18:47:46 UTC