W3C home > Mailing lists > Public > xmlschema-dev@w3.org > May 2001

Re: Time Zones and XML Schema date types

From: Jeff Rafter <jeffrafter@definedweb.com>
Date: Tue, 8 May 2001 20:13:55 -0700
Message-ID: <00a101c0d836$15125350$f181fea9@lazarus>
To: "Ashok Malhotra" <ashokma@microsoft.com>
Cc: <xmlschema-dev@w3.org>
>Consider a date like May 8, 2001.  This is actually a period of 24 hours
>(roughly).  The exact time the period starts and ends depends on the
>time zone.  So, I think, its clear why such types need a timezone.

Understanding both types as periods of time certainly does help, thanks.

>What is more controversial is why we allow dates without a timezone.
>This is to conform with SQL and also common usage.  Yes, it makes
>comparing dates with and without time zones complicated.

Is this a case where the common usage should outweigh other concerns,
especially when common usage includes an international standard?  It seems
as though XML Schema could have avoided adding to the ISO spec in this gray
area by simply allowing implementations to assume GMT-- though I am even a
little fuzzy with how I think this would work.  Essentially, isn't it safe
to presume (although the XML Schema spec prohibits it):

1999-01-16 = 1999-01-16T00:00:00Z

Assuming that 1999-01-16 is the 16th of January 1999-- shouldn't it follow
that the starting instant of the date *is* 00:00:00Z?  I suppose not, I am
faltering back and forth between a day is 24 hours (roguhly) beginning in
timezone X and a day begins when the international date line is crossed. I
am sure all of this has been thought through already (probably for many
years now).

Thanks again,
Jeff Rafter
Defined Systems
http://www.defined.net
XML Development and Developer Web Hosting
Received on Tuesday, 8 May 2001 23:14:21 GMT

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