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RE: Year 0000

From: Ashok Malhotra <ashokma@microsoft.com>
Date: Mon, 3 Sep 2001 15:33:51 -0700
Message-ID: <E5B814702B65CB4DA51644580E4853FB90736F@red-msg-12.redmond.corp.microsoft.com>
To: <zongaro@ca.ibm.com>, "Andrew Layman" <andrewl@microsoft.com>
Cc: <lmartin@ca.ibm.com>, <www-xml-schema-comments@w3.org>, <w3-xml-schema-wg@w3.org>
Henry:
Your response to Andrew was not quite accurate.  ISO 8601 and XML Schema
use what is called the "prolaptic Gregorian calendar".  This means they
refer to years, months, etc as if the Gregorian calendar had been in use
since the beginning of time; specifically before 1582.  If you take this
viewpoint there is no discontinuity.
 
ISO 8601 in its usual cryptic fashion says (section 4.3.2.1 Note 2)
'Also note that the year numbers for years before the year [0001] differ
from the year numbers in the "BC/AD calendar system", where the year"1
BC" is followed by the year "1 AD"'   The Encarta article on calendars
http://encarta.msn.com/find/Concise.asp?z=1&pg=2&ti=761560321&cid=8#p8
says that "The Gregorian calendar is also called the Christian calendar
because it uses the birth of Jesus Christ as a starting date. "  So, the
BC/AD calendar, I assume from the above, uses Gregorian years.  Thus,
year [0001] corresponds to AD 1 and ... this is my interpretation ...
year [0000] corresponds to 1 BC and so on.  This is consistent if a bit
weird.
 
BTW, your notes appear in tiny font.  I assume this is some idiosyncracy
of Lotus Notes.
 
All the best, Ashok

	-----Original Message----- 
	From: zongaro@ca.ibm.com 
	Sent: Mon 8/27/2001 6:25 AM 
	To: Andrew Layman 
	Cc: lmartin@ca.ibm.com; Ashok Malhotra;
www-xml-schema-comments@w3.org; w3-xml-schema-wg@w3.org 
	Subject: RE: Year 0000
	
	

	
	Hi Andrew, 
	
	     Perhaps I was a bit imprecise in saying that the year 0000
in ISO 8601 is what is commonly called 1 BCE.  The year 1 BCE is a year
in the Julian calendar, whereas ISO 8601 treats the Gregorian calendar
as if it existed prior to 1582-10-15, and extends it indefinitely back
in time.  So 0000 in ISO 8601 and 1 BCE overlap to a great extent, but
not necessarily completely. 
	
	     1582-10-05 is the day after 1582-10-04, and 1582-10-14 is
the day before 1582-10-15 in ISO 8601.
	
	Thanks,
	
	Henry
	
------------------------------------------------------------------------
	Henry Zongaro      XML Parsers development
	IBM SWS Toronto Lab   Tie Line 778-6044;  Phone (416) 448-6044
	mailto:zongaro@ca.ibm.com
	

	Please respond to "Andrew Layman" <andrewl@microsoft.com> 

	To:        Lisa Martin/Toronto/IBM@IBMCA, "Ashok Malhotra"
<ashokma@microsoft.com> 
	cc:        Henry Zongaro/Toronto/IBM@IBMCA,
<www-xml-schema-comments@w3.org>, <w3-xml-schema-wg@w3.org> 
	Subject:        RE: Year 0000 
	
	
	In that case, is 1582-10-05 a valid ISO 8601 date?  What day
follows
	1582-10-04?  What day precedes 1582-10-15?  Are the answers to
these
	questions consistent with the assumption that year 0000 is 1
BCE?
	
	-----Original Message-----
	From: lmartin@ca.ibm.com [mailto:lmartin@ca.ibm.com] 
	Sent: Friday, August 10, 2001 2:08 PM
	To: Ashok Malhotra
	Cc: zongaro@ca.ibm.com; www-xml-schema-comments@w3.org;
	w3-xml-schema-wg@w3.org
	Subject: RE: Year 0000
	
	
	Yes, I'll add it to our Issues list.
	Lisa.
	
	
	"Ashok Malhotra" <ashokma@microsoft.com> on 08/10/2001 04:11:14
PM
	
	Please respond to "Ashok Malhotra" <ashokma@microsoft.com>
	
	To:   Henry Zongaro/Toronto/IBM@IBMCA
	cc:   <www-xml-schema-comments@w3.org>,
<w3-xml-schema-wg@w3.org>, Lisa
	     Martin/Toronto/IBM@IBMCA
	Subject:  RE: Year 0000
	
	
	Yes, I came to the same conclusion after rereading the 2000
version of
	ISO 8601. I think we need to consider this as a possible errata
item.
	Lisa, can you please add to the errata list.
	
	
	
	All the best, Ashok
	===========================================================
	
	    -----Original Message-----
	    From: zongaro@ca.ibm.com [mailto:zongaro@ca.ibm.com]
	    Sent: Friday, August 10, 2001 1:01 PM
	    To: Ashok Malhotra
	    Cc: www-xml-schema-comments@w3.org; w3-xml-schema-wg@w3.org;
	    lmartin@ca.ibm.com
	    Subject: RE: Year 0000
	
	
	
	    Hi Ashok,
	
	         Although ISO 8601:2000 isn't entirely clear on the
point, it
	does
	    say that the year numbers are contiguous.  I take that to
mean that
	    0000 is the year before 0001, and -0001 is the year before
that.
	That
	    would mean 0000 is what is usually referred to as 1 BC (or 1
BCE)
	and
	    -0001 is 2 BC (or 2 BCE).
	
	         If my understanding is correct, that means the years
that are
	    commonly called 1BC (0000) and 5BC (-0004) are leap years in
the
	    proleptic Gregorian calendar, but 4BC (-0003) is not.
	
	    Thanks,
	
	    Henry
	
	
------------------------------------------------------------------------
	
	    Henry Zongaro      XML Parsers development
	    IBM SWS Toronto Lab   Tie Line 778-6044;  Phone (416)
448-6044
	    mailto:zongaro@ca.ibm.com
	
	
	    Please respond to "Ashok Malhotra" <ashokma@microsoft.com>
	
	
	    To:        Henry Zongaro/Toronto/IBM@IBMCA,
	    <www-xml-schema-comments@w3.org>
	    cc:        <w3-xml-schema-wg@w3.org>, Lisa
Martin/Toronto/IBM@IBMCA
	    Subject:        RE: Year 0000
	
	
	    I found additional confirmation that the 2000 version of ISO
8601
	    does,
	    indeed, allow the year 0000.  I don't know what it maps to
in terms
	on
	    AD and BC because AD 1 == 0001 and BC 1 == -0001.  Should we
	discuss
	    as
	    a possible errata item.
	    Ashok
	
	                    -----Original Message-----
	                    From: zongaro@ca.ibm.com
	                    Sent: Thu 8/9/2001 2:02 PM
	                    To: www-xml-schema-comments@w3.org
	                    Cc:
	                    Subject: Year 0000
	
	
	
	
	                    Hello,
	
	                         I just saw a copy of ISO 8601:2000.  I
was
	    surprised to
	    discover that it defines 0000 to be a valid year, unlike the
	    specification of dateTime in the "XML Schema:  Datatypes"
	    recommendation
	    [1].  I gather that in ISO 8601:2000, the year 0000 is
roughly 
	     equivalent to what people usually refer to as 1BC, and is a
leap
	year.
	
	                         Should dateTime follow ISO 8601:2000 in
this
	    respect?
	
	                    Thanks,
	
	                    Henry
	                    [1]
	    http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/#dateTime
	
	
	
------------------------------------------------------------------------
	
	                    Henry Zongaro      XML Parsers development
	                    IBM SWS Toronto Lab   Tie Line 778-6044;
Phone
	(416)
	    448-6044
	                    mailto:zongaro@ca.ibm.com
	
	
	
	
	
	
	
Received on Monday, 3 September 2001 18:34:26 GMT

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