[tz] What's "right"?

Michael H Deckers michael.h.deckers at googlemail.com
Mon Nov 16 10:29:43 UTC 2020

On 2020-11-15 23:21, John Sauter wrote:
> If I am reading section 9.4 correctly, they are defining two time
> scales: the old scale (before the leap second) and the scale after the
> step.  In the old scale the leap second at the end of 2016 would start
> at 2016-12-31T24:00:00 and end at 2016-12-31:24:00:01.  In the scale
> after the step the leap second would start at 2017-01-01:00:00:-1 and
> end at 2017-01-01T00:00:00.


     The rationale of a positive leap second notation for a time point
     is to indicate that the point does not belong to the normal range
     of datetime values, where there are only 20 seconds from
     2016-12-31T23:59:50 to 2017-01-01T00:00:10. One therefore has
     to use a notation that cannot be confused with notations that
     are used for these normal datetime values.

     Exceeding the normal range [0..1[ d of time of day is one
     method; the ITU method uses times of day >= 1 day, but times
     of day < 0 d could similarly be used. Other means would be
     affixes to the notation (such as the leap second bit in the
     Ada programming language, or the labels "A", "B" proposed to
     distinguish duplicate timestamps during fall back from summer
     time in Denmark and Germany).

     Michael Deckers.


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