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Re: XML-like date/time support ?


From: Paul Eggert
Subject: Re: XML-like date/time support ?
Date: Sun, 08 Jan 2006 16:24:26 -0800
User-agent: Gnus/5.1007 (Gnus v5.10.7) Emacs/21.4 (gnu/linux)

Nicolas Mailhot <address@hidden> writes:

> The XML folks have defined a single common international date/time
> format

I just looked at <http://www.w3.org/TR/NOTE-datetime> and it appears that

(1) There are 9 formats, not 1.

(2) There is no way to represent a leap second.  This is not normally
    a problem, since few coreutils hosts handle leap seconds
    correctly, but for those hosts that do I suppose we can just
    ignore the XML standard.

(3) There is no way to represent time zone offsets that are not a
    multiple of a minute, or years before 0000 or after 9999, or a few
    other things like that.  But I suppose they are just inheriting
    these limitations from ISO 8601.

I suppose we can add an option for this, with an operand to specify
which of the 9 formats you want.  Something like the existing "date
--rfc-3339=TIMESPEC".

But I'm a bit leery of calling it "date --xml=TIMESPEC", or "date
--w3c=TIMESPEC".  These guys might change their mind some day in the
future.  Is there some more-specific name we can use, that XML folks
would recognize?

Also, I see a slightly different set of rules in
<http://www.w3.org/TR/xmlschema-2/> (2004-10-28), section 3.2.7.  For
example, it says that a canonical representation cannot use the time
zone "+00:00", and that fractional seconds cannot end in "0", and that
the time zone is optional.  What gives?  This document looks far more
official: does it supersede the document you mentioned?  Should "date"
output a canonical representation?

I guess that might mean that there are 10 XML formats instead of 9?
Or even more, if non-canonical formats are desired?  Sorry, I'm a bit
lost here.




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