[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).
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