Re: Length of a day.

Frank Olken at LBNL wrote:

> 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.). 


So, W3C XML Schema is here at variance with ISO 8601 to be more 
conforming to UTC (and solar time)!

> Note that leap seconds screw up minutes, 
> hours and days.


Yes, and doesn't this means that the algorithm that add durations to 
dateTimes and considers that there are only two groups of values 
"Essentially, this calculation is equivalent to separating D into 
<year,month> and <day,hour,minute,second> fields" is not 100% exact?

This algorithm considers that the only variable quotients between 
datetime parts is between the groups <year,month> and 
<day,hour,minute,second> and from what you're saying, there should be 
three groups: <year,month>, <day> and <hour,minute,second>.


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


Yes!


>                             Frank Olken, LBNL,  olken@lbl.gov


Thanks for the explanation.

Eric
-- 
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Eric van der Vlist       http://xmlfr.org            http://dyomedea.com
http://xsltunit.org      http://4xt.org           http://examplotron.org
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Received on Monday, 29 October 2001 11:14:37 UTC