bug#22034: time-utc->date shows bogus zone-dependent leap second

[John Cowan <cowan@ccil.org>]

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On Sat, Oct 20, 2018 at 5:43 PM Mark H Weaver <mhw@netris.org> wrote:

If I understand correctly, 'time-utc->date' should never return a date
> object with 60 in the seconds field, because those extra seconds have no
> representation in time-utc.  They only have representations in time-tai
> and time-monotonic.
>

As I understand it, this is incorrect.  UTC days can contain either 86400
or 86401 seconds (or in principle a different number), depending on whether
the day has a leap second.  It is *Posix* time, not UTC time, that contains
a fixed number of seconds per day, or more accurately that assigns a label
from 0 to 864399 to the seconds of a day, and can assign the same label to
more than one second (or in principle could assign one or more labels to no
second) on a leap-second day. Consequently, a broken-down time can indeed
return 60 in the seconds field, but only for a UTC clock, never for a Posix
clock.

This error is repeated in a number of your later messages, but I'll respond
only to this one.

-- 
John Cowan          http://vrici.lojban.org/~cowan        cowan@ccil.org
Tautology is something that is tautological.  --Francois-Rene Rideau

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