- From: <zongaro@ca.ibm.com>
- Date: Tue, 4 Sep 2001 10:21:33 -0400
- To: "Ashok Malhotra" <ashokma@microsoft.com>
- Cc: "Andrew Layman" <andrewl@microsoft.com>, lmartin@ca.ibm.com, <www-xml-schema-comments@w3.org>, <w3-xml-schema-wg@w3.org>
- Message-ID: <OFE158C983.E2D87C31-ON85256ABD.0048CC27@torolab.ibm.com>
Hi Ashok,
Sorry if my note seemed to imply that there was a discontinuity in
the Gregorian calendar. It certainly wasn't intended. In particular, I
was trying to indicate that there are no days ommitted from October, 1582
in the proleptic Gregorian calendar; i.e., it's a month of 31 days, just
like any other October rather than a month of 21 days.
As for whether AD 1 is a date in the Gregorian or Julian calendar, I
was describing common usage. When one reads, for instance, that Miguel de
Cervantes was born on October 9, 1547, that's a date in the Julian
calendar; the same date in the proleptic Gregorian calendar is October 19,
1547. To the best of my knowledge, historians don't usually translate
dates prior to 1582 into the Gregorian calendar, though they might need to
for dates after 1582, prior to the Gregorian calendar's widespread
adoption.
Dates in the proleptic Gregorian calendar coincide with dates in the
Julian calendar between March 1, 200 and February 28, 300. Outside of
that range they diverge. The year 0000 in ISO 8601 is the year 1 BC in
the proleptic Gregorian calendar, but it's not the 1 BC of historians or
of common usage, which is a year in the Julian calendar. It seemed to me
that that was the question Andrew was asking.
Historians using dateTime and the related data types will have to be
aware of the difference.
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, "Andrew Layman" <andrewl@microsoft.com>
cc: Lisa Martin/Toronto/IBM@IBMCA, <www-xml-schema-comments@w3.org>,
<w3-xml-schema-wg@w3.org>
Subject: RE: Year 0000
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 Tuesday, 4 September 2001 10:21:36 UTC