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Re: Length of a day.

From: Frank Olken at LBNL <olken@lbl.gov>
Date: Mon, 29 Oct 2001 07:55:34 -0800
Message-ID: <3BDD7BF6.1090707@lbl.gov>
To: Eric van der Vlist <vdv@dyomedea.com>
CC: www-xml-schema-comments@w3.org, olken@lbl.gov
Not all days have (exactly) 24 hours.  If we are using Universal 
Coordinated Time (UTC) (which most of
world is)  -  then some
days have an extra second (leap second) added to try to keep UTC time in 
synch with solar time.  ISO 8601
is at variance with the UTC time conventions.  (There is another kind of 
time - Universal Atomic Time -
which simply counts seconds since some fixed time mark - however this is 
primarily used only by folks
tracking satellites, etc.).  Note that leap seconds screw up minutes, 
hours and days.

It is also the case that dates really should carry time zone 
designations, if they are to refer to a 24hour
period.

                            Frank Olken, LBNL,  olken@lbl.gov

Eric van der Vlist wrote:

> I wonder if the W3C XML Schema recommendation is conform to ISO 8601 
> on the issue of the length of a day.
>
> W3C XML Schema:
> --------------
>
> 3.2.9 date
>
> [Definition:]  date represents a calendar date. The ˇvalue spaceˇ of 
> date is the set of Gregorian calendar dates as defined in § 5.2.1 of 
> [ISO 8601]. Specifically, it is a set of one-day long, non-periodic 
> instances e.g. lexical 1999-10-26 to represent the calendar date 
> 1999-10-26, independent of how many hours this day has.
>
> ISO 8601:
> --------
> § 5.2.1 doesn't say what a "date" is, but this is defined in the "3 
> Terms and definition":
>
> 3.3 date, calendar: A particuliar day of the calendar year
>
> and
>
> 3.5 day: A period of 24 hours starting at 0000 and ending at 2400
>
> Eric
Received on Monday, 29 October 2001 10:45:40 GMT

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