- From: Ashok Malhotra <ashokma@microsoft.com>
- Date: Thu, 12 Dec 2002 08:05:53 -0800
- To: "Schluter, Paul (MED, GEMS-IT)" <Paul.Schluter@med.ge.com>, "W3C XML Schema Comments list" <www-xml-schema-comments@w3.org>
- Cc: <jjc@jclark.com>
Paul: Please look at Appendix D. This allows '60' for the seconds value and has an explanation re. leap seconds. This may cover what you need. All the best, Ashok -----Original Message----- From: Schluter, Paul (MED, GEMS-IT) [mailto:Paul.Schluter@med.ge.com] Sent: Thursday, December 12, 2002 7:46 AM To: Ashok Malhotra; W3C XML Schema Comments list Cc: 'jjc@jclark.com'; Schluter, Paul (MED, GEMS-IT) Subject: RE: 24:00:00 allowed or not Thursday, December 12, 2002, Ashok, You are absolutely correct, and that was something I realized right after I sent you the email. We want to use "24:00:00" strictly as an alternative representation for "00:00:00". We should encode the (positive) leap second as "60", as in "23:59:60" (Zulu). This is supported by the ISO 8601 time-date standard. I've included the ISO 8601 definitions for a 'leap second' and 'time of day' below, which is consistent with above proposal. Here are examples of the various 'leap-second' transitions that would occur in the Zulu (GMT 00:00) time zone: NO LEAP SECOND ADJUSTMENT (last minute has 60 seconds) 2001-06-30T23:59:58Z 2001-06-30T23:59:59Z 2001-07-01T00:00:00Z 2001-07-01T00:00:01Z LEAP SECOND INSERTION (+ last minute has 61 seconds) 1998-12-31T23:59:58Z 1998-12-31T23:59:59Z 1998-12-31T23:59:60Z 1999-01-01T00:00:00Z 1999-01-01T00:00:01Z LEAP SECOND DELETION (- last minute has 59 seconds) XXXX-06-30T23:59:58Z XXXX-07-01T00:00:00Z XXXX-07-01T00:00:01Z [Note: this has never happened!] It should be noted that the leap-second is declared at midnight in the "Z" (GMT) timezone and is applied to all other timezones at that single instant of time. Thus, the (inserted) leap-second indicator of "60" would appear at civil (local) times different than midnight. So, at Chicago O'Hare airport, we would have an ISO 8601 formatted timestamp of "1998-12-31T17:59:60-6:00" (CST) for the leap second insertion that occurred on December 31, 1998. I hope this helps. I believe it is important to have the option of expressing leap-seconds so that we can ensure a rigorous 1:1 mapping between and XML/UTC timestamps and NTP or equivalent timestamps that utilize a strictly isochronous seconds counter. Best regards, Paul Schluter - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - From ISO8601:2000(E) 3.25 [definition of] second, leap Intentional time step of one second used to adjust UTC to ensure approximate agreement with UT1 (a time scale based on the rotation of the Earth); an inserted second is called positive leap second and an omitted second is called negative leap second (see ITU-R Rec.TF.460-5) NOTE A positive leap second is inserted between 23:59:59Z and 24:00:00Z and can be represented as 23:59:60Z. Negative leap seconds are achieved by the omission of 23:59:59Z. Insertion or omission takes place as determined by IERS, normally on June 30th or December 31st, but if necessary on March 31st or September 30th. 5.3 Time of the day As this International Standard is based on the 24-hour timekeeping system that is now in common use, hours are represented by two digits from [00] to [24], minutes are represented by two digits from [00] to [59], and seconds are represented by two digits from [00] to [60]. For most purposes, times will be represented by four digits [hhmm]. The representation of the hour by [24] is only allowed to indicate midnight, see 5.3.2. The representation of the second by [60] is only allowed to indicate the positive leap second or a time-point within that second. =========================================================== -----Original Message----- From: Ashok Malhotra [mailto:ashokma@microsoft.com] Sent: Thursday, December 12, 2002 7:16 AM To: Schluter, Paul (MED, GEMS-IT); W3C XML Schema Comments list Subject: RE: 24:00:00 allowed or not Paul: As the attached note says 24:00:00 is allowed. But it also says that it is an alternate representation for 00:00:00 (of the following day). This is not what you want. In the presence of a leap second you want 24:00:00 to be the final second of the current day and 00:00:00 the following second of the next day. We need to craft some careful wording to cover this situation. All the best, Ashok =========================================================== -----Original Message----- From: Schluter, Paul (MED, GEMS-IT) [mailto:Paul.Schluter@med.ge.com] Sent: Wednesday, December 11, 2002 4:59 PM To: W3C XML Schema Comments list Subject: RE: 24:00:00 allowed or not Wednesday, December 11, 2002, Ashok and James, I noticed this thread in the W3C email archives regarding whether 24:00:00 should be allowed or not. It _must_ be allowed, because the time "24:00:00" can actually exist when a leap-second is inserted at midnight. Leap-second insertion typically occurs every 18 months or so, principally to account for the gradual slowing of the earth's rotation over time (roughly 1.7 msec/day/century). Leap seconds are supported by NTP (RFC-1305) and SNTP (RFC-2030) and are recognized in numerous other areas such as astronomy where accurate timekeeping is required. Regards, Paul Schluter =========================================================== Date: Tue, 23 Apr 2002 06:40:06 -0700 Message-ID: <E5B814702B65CB4DA51644580E4853FB019EEB02@red-msg-12.redmond.corp.micros oft.com> From: "Ashok Malhotra" <ashokma@microsoft.com> To: "James Clark" <jjc@jclark.com>, <www-xml-schema-comments@w3.org> Subject: RE: 24:00:00 allowed or not? 24:00:00 is allowed. It is an alternate representation for 00:00:00 All the best, Ashok =========================================================== -----Original Message----- From: James Clark [mailto:jjc@jclark.com] Sent: Tuesday, April 23, 2002 6:19 AM To: www-xml-schema-comments@w3.org Subject: 24:00:00 allowed or not? ISO 8601 section 5.3.2 allows 24:00:00 as a representation of midnight. Appendix D of XML Schema Part 2 says that the hh field runs between 0 and 23, but there is no mention of 24:00:00's not being allowed as a difference between XML Schema and ISO 8601. I'm left uncertain as to whether 24:00:00 is allowed or not. James
Received on Thursday, 12 December 2002 11:06:38 UTC