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Re: [ISO8601] Calculating using ordinal dates

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  • BudaiEndreIstvan
    ... From: Daniel Biddle To: ISO8601@yahoogroups.com Sent: 2003 03 05 00:40 Subject: [ISO8601] Calculating using ordinal dates ... And indeed computers
    Message 1 of 5 , Mar 5, 2003
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      ----- Original Message -----
      Sent: 2003 03 05 00:40
      Subject: [ISO8601] Calculating using ordinal dates
      > "ali0917 " wrote:
      > > Why do ordinal dates exist anyway?
      >
      > Because they're useful sometimes, though not typically in day-to-day
      > use. [...]
      > If you separate out the year part and treat the year length properly
      > then all other date/time manipulations can be done with simple
      > subtraction (give or take the effect of leap-seconds which can be
      > significant in this application).

      And indeed computers routinely store and process ordinal dates/times
      counted in days or seconds from an agreed point in time (such as the
      start of 1970), because that is so much easier than dealing with human
      representations (even ISO 8601).

      As I write this, my system's clock reads 1046791407 seconds, and it
      continues counting up by one each second, not needing to know anything
      about calendars, clocks, time zones or leap seconds.

      If the system needs to display a date or time for my benefit, another
      layer of software:
       * divides the ordinal time into years, months, days, hours, minutes,
         seconds, day-of-week, day-of-year;
       * looks up and applies appropriate time zone and leap second
         adjustments;
       * looks up my preferred date and time format;

       * if necessary, looks up the names of the month and day and ordinal
         suffixes ("st/nd/rd/th") in my preferred language;

       * and passes the formatted, padded, converted, translated, and adjusted
         result to whatever requires it.

      As you might imagine, this is slow. In contrast, arithmetic with ordinal
      times is extremely fast.

      Daniel Biddle
      *I need to address the ordinal suffixes of the English and French languages, both of which are awkward and causing headaches to learners of either tongue.    A common practice in many fields is to replace the suffixes with a dot, not unlike the chapters of a book or page numbering of publications.
       
      First    or   Premiere     1.                    [instead of 1st or 1ere]   
      Second    Deuxieme    2.                            [2nd or 2eme]
      Twenty-third    --     23.                            [23rd or 23eme]
      Fifty-fourth    --        54.                            [54th or 54eme]
      The advantages can be seen especially in Canada where both of those official languages exist side by side.    The dot automatically indicates an ordinal number and eliminates the need for repeating each number in two languages.
       
      BUDAI  Andrew



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