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1852Re: [ISO8601] Re: Wow, no posts for a long time

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  • Michael Deckers
    Sep 21 8:55 AM
      On 2006-09-18, piebaldconsult wrote:

      > > [d] A Note to the definition of "duration" says that leap seconds
      > > must be "accounted" for in the length of epoch intervals.
      > Which section of which version? I don't see that verbiage.

      You are perfectly right, I stand corrected. I should not have put
      the word, "accounted", within quotes.

      > Section 2.1.6 in version :2004 has
      > "
      > NOTE 1 In the case of discontinuities in the time scale, such as a leap
      > second or the change from winter time to summer time and back, the
      > computation of the duration requires the subtraction or addition of the
      > change of duration of the discontinuity.
      > "
      > Although that seems pretty clearly to support your question, I could
      > still argue that it doesn't, that it's not clear, and that I can twist
      > it to my own devious ends.

      Of course you can. The question is whether it can be done while
      still conforming with ISO 8601:2004. There are two reasons in favor:
      First, this is just a Note, and as such it does not constitute a
      normative requirement of ISO 8601.
      Second, there is a (normative) sentence [1 p12]:
      This International Standard does not assign any particular
      meaning or interpretation to any data element that uses
      representations in accordance with this International
      Standard. Such meaning will be determined by the context of
      the application.

      Nevertheless, the standard must assign _some_ meaning to its notations,
      and so it does. It states (again in a Note in [2.2.2]) that
      2005-12-31T23:59:60Z is one second before 2005-12-31T24:00:00Z.
      The standard seems to require that the duration of the time interval
      is PT02S, I have to assume.

      > Given 23:55:00 and adding PT10M for most nights will result in
      > 00:05:00, but on a leap-second night we have to consider the
      > possibility that the result is 00:04:59, yes?

      For UTC timestamps, I think that's what the standard says, yes.
      Other timescales, such as UT or TAI or GPS time or TCG do not
      have leap seconds, only UTC and its translates (zone times) do.

      > I, for one, don't want that result, so I'll add the "duration of the
      > discontinuity" of the leap second as required, yielding the value I
      > _do_ want (00:05:00) even though there may be some who'd argue that
      > that's wrong. I can certainly see their point, but I'm still going to
      > do whatever a darn well please, it won't matter in most applications.

      Nor do I want that result with UTC in most, if not all, cases. I am
      just not sure whether this would still conform with ISO 8601:2004.


      Michael Deckers
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