- From: Andrew Layman <andrewl@microsoft.com>
- Date: Wed, 5 Sep 2001 11:58:59 -0700
- To: <zongaro@ca.ibm.com>, "Ashok Malhotra" <ashokma@microsoft.com>
- Cc: <lmartin@ca.ibm.com>, <www-xml-schema-comments@w3.org>, <w3-xml-schema-wg@w3.org>
- Message-ID: <C3729BBB6099B344834634EC67DE4AE102623AF1@red-msg-01.redmond.corp.microsoft.com>
Thank you for your detailed answers. This seems worthy to appear as a footnote to the XML Schema specification to clear up misunderstandings that might easily appear since the mapping from lexical space to value space will sometimes not match naive expectations. -----Original Message----- From: zongaro@ca.ibm.com [mailto:zongaro@ca.ibm.com] Sent: Tuesday, September 04, 2001 7:22 AM To: Ashok Malhotra Cc: Andrew Layman; lmartin@ca.ibm.com; www-xml-schema-comments@w3.org; w3-xml-schema-wg@w3.org Subject: RE: Year 0000 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 Wednesday, 5 September 2001 15:00:50 UTC