Though I have been reluctant to write a profile of [ISO 8601], the W3C HTML WG has decided it wants the spec for Cougar (the next version of HTML) to reference a date/time profile and I've been actioned to produce this profile by the end of next week. This note lists some preliminary thoughts for comment. If you want to find out more about [ISO 8601], visit [KUHN]. I wrote a few days ago that my goal is a profile which is: - conformant, - widely adopted, - easy to understand, - not too permissive, - not too restrictive, - electronically available. The way to reconcile some of these requirements is to provide a profile allowing several options, especially regarding granularity. Other standards could refer to the profile and state which option has/have been adopted. A rough sketch follows. I have borrowed some phrases from [KUHN]. Granularity =========== This profile of [ISO 8601] defines four levels of granularity: 1. Date only ------------- The format is: YYYY-MM-DD 2. Date plus hours and minutes ------------------------------- The format is one of: YYYY-MM-DDThh:mmZ YYYY-MM-DDThh:mm+hh:mm YYYY-MM-DDThh:mm-hh:mm where: Z indicates that the date/time uses Universal Time (UTC), +hh:mm indicates that the date/time uses a local time zone which is "hh" hours and "mm" minutes ahead of UTC, -hh:mm indicates that the date/time uses a local time zone which is "hh" hours and "mm" minutes behind UTC. 3. Date plus hours, minutes and seconds ---------------------------------------- The format is one of: YYYY-MM-DDThh:mm:ssZ YYYY-MM-DDThh:mm:ss+hh:mm YYYY-MM-DDThh:mm:ss-hh:mm 4. Date plus hours, minutes, seconds and decimal fractions of seconds ---------------------------------------------------------------------- The format is one of those shown in option 3, with the insertion, immediately after "ss", of either a full stop or a comma, followed immediately by one or more digits representing a decimal fraction of a second, eg: YYYY-MM-DDThh:mm:ss.ddZ YYYY-MM-DDThh:mm:ss.dd+hh:mm YYYY-MM-DDThh:mm:ss.dd-hh:mm If adopting this granularity option, the adopting standard must state how many digits may be used to represent a decimal fraction of a second, eg: 2 digits, 1-3 digits, 1-99 digits, any number of digits. Treatment of missing elements ============================= In some cases, software components may need to compare a date/time using coarser granularity with one using finer granularity. This shall be done as described below. Granularity options 2-4 ----------------------- The missing portions are deemed to be equal to zero. Thus the following all represent the same date/time: 1997-06-20T12:34Z 1997-06-20T12:34:00Z 1997-06-20T12:34:00.00Z 1997-06-20T12:34:00.000000000000000000000000000Z Granularity option 1 -------------------- An isolated date is treated as if it had the following string appended: T12:00Z For example: 1997-06-20 is treated as if it were: 1997-06-20T12:00Z This approach, proposed by Charles Wicksteed, has the advantage that at 1997-06-20T12:00Z, most of the world would agree that the current date is 1997-06-20. Comments? ~~~ [ISO 8601] "Data elements and interchange formats -- Information interchange -- Representation of dates and times", ISO 8601:1988(E), International Organization for Standardization, June, 1988. [KUHN] "A Summary of the International Standard Date and Time Notation", Markus Kuhn, <http://www.ft.uni-erlangen.de/~mskuhn/iso-time.html>, 1996-11-05. [NEWMAN] "Date and Time on the Internet", Chris Newman, <draft-newman-datetime-01.txt>, January 1997. ----------------------------------------------------------------------- Misha Wolf Email: misha.wolf@reuters.com 85 Fleet Street Standards Manager Voice: +44 171 542 6722 London EC4P 4AJ Reuters Limited Fax : +44 171 542 8314 UK ------------------------------------------------------------------------ Any views expressed in this message are those of the individual sender, except where the sender specifically states them to be the views of Reuters Ltd.