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2198Re: [ISO8601] UTC didn't exist before 1961

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  • Deckers, Michael
    Jun 2, 2009
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      On 2009-05-26, pqrc96 penned thusly:

      > In the future, I will not emit ISO 8601 dates with a Z suffix or a time zone
      > unless the date is on or after January 1, 1972, the date of the formal
      > adoption of the name Coordinated Universal Time. I will reject incoming dates
      > in that format if I am able to determine that time zones had not been adopted
      > in the place in question on the date stated. I will reject incoming dates
      > with a time zone offset that is not a multiple of 15 minutes.

      That's fine if your application imposes such restrictions, but it is
      not what ISO 8601 requires.

      ISO 8601 fixes some notations but it does not constrain the meaning of
      these notations. Other standards employ some of these notations and
      endow them with specific semantics.

      For ISO 8601 timestamps with and without time zone differences,
      XML Schema ([http://www.w3.org/TR/xmlschema11-2/%5d) is an example. It
      defines several operations with these timestamps (such as comparison and
      difference), and gives the semantics of these timestamps as "points on
      a time line". This is very general, and makes these notations
      usable for expressing epochs in all kinds of time scales, not just UTC
      and zone times: navigators can use it for GPS time, astronomers for TCB,
      and historians for apparent solar time at Jerusalem.

      Of course it is possible to further restrict the meaning to mean
      solar time and the civil zone times introduced since 1895, or even to
      time scales based on TAI, but this is not required by ISO 8601.

      Michael Deckers
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