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Re: 2000-01-01+13:00 and 1999-12-31ˆ’11 :00 are equal?

From: G. Ken Holman <gkholman@CraneSoftwrights.com>
Date: Mon, 17 Sep 2012 16:45:23 -0400
Message-Id: <7.0.1.0.2.20120917164301.023ce8a8@wheresmymailserver.com>
To: "xmlschema-dev@w3.org" <xmlschema-dev@w3.org>
At 2012-09-17 19:31 +0000, Costello, Roger L. wrote:
>Hi Folks,
>
>In the XSD 1.1 data types specification it says 
>this in the discussion of the "date" data type:
>
>     Some date values with different time zone offsets
>     that were identical in the 1.0 version of this
>     specification, such as 2000-01-01+13:00 and
>     1999-12-31ˆ’11:00, are in this version of this
>     specification equal ...
>
>That seems to be a mistake.
>
>How can adding 13 hours onto January 1, 2000 
>equal December 31, 1999 minus 11 hours?

Please see my answer to your question in the XSLT list:

   http://markmail.org/message/yviln2nbh4ehm2vo

The characters "+" and "-" are not arithmetic 
operators ... there is no addition or subtraction 
going on.  The characters are part of the time zone indicators.

So the text you quoted is correct:  it is, in 
fact, the text you quoted continues on to say 
"(because they begin at the same moment on the 
time line)" because there is a moment when it is 
1999-12-31 in the -11:00 time zone (Midway) that 
it is 2000-01-01 in the +13 time zone 
(Tonga).  And you are only talking edge cases with distant values from UTC.

I hope this helps understand the notation of ISO 8601:

   http://en.wikipedia.org/wiki/ISO_8601

. . . . . . . . Ken


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Received on Monday, 17 September 2012 20:52:29 GMT

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