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1289Re: New version ISO 8601:2005 released 2005-04-01

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  • John Hynes
    Apr 1 7:38 PM
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      --- John Steele <johnmsteele@y...> wrote:
      > I'm sure astronmers everywhere would have preferred Julian Days, ie
      > 245 3461.500

      Astronomers also use Gregorian dates, in year-month-day order, with
      the fractional day added to the ordinal day of month. For instance,
      the standard epoch J2000.0 is often represented as 2000 January 1.5,
      which would be 2000-01-01,5 in ISO format. I can provide many
      examples online. Also, NASA and NORAD publish epoch dates of orbital
      elements of artificial satellites as ordinal dates with fractional day
      added, e.g. the same date is represented as 00001.50000000. (Still
      with two-digit year, unfortunately.) It would make sense to
      incorporate this practice by astronomers into ISO 8601. Although the
      month is usually spelled out or abbreviated, the month number is also
      used sometime. The ISO standard does cover decimal fractions of
      hours, minutes and seconds, but not days.

      I suppose that Julian Dates could be added to the ISO 8601 standard,
      but that would seem unnecessary, since they are represented simply as
      a single decimal number. It would be a short section. I think that
      fractional day s are used by astronomers, instead of HMS, for ease in
      calculations, including the converstion to/from JD/MJD. Julian Days
      and Julian Dates, as well as Modified Julian Dates, already are
      covered by a standard, IAUGA XXIII Resolution B1.

      And if anybody hasn't figured it out by now, April Fool! I figured
      that this group might get a kick out of it. :)

      John
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