[ntp:questions] Leap second to be introduced in June
unruh at invalid.ca
Wed Jan 14 17:48:42 UTC 2015
On 2015-01-14, Erwan David <erwan at rail.eu.org> wrote:
> Harlan Stenn <stenn at ntp.org> disait le 01/13/15 que :
>> Martin Burnicki writes:
>>> Terje Mathisen wrote:
>>>> I hate to admit it, but I'm starting to believe Google's approach,
>>>> where they smear the leap second over something like a day, might be
>>>> one of the better workarounds.
>> This won't work for a bunch of folks. Other folks *hate* this approach
>> because it means that during this 24-hour period the reported time is
>> off by both frequency *and* offset.
> WHat problem withsaying that one minute is between 58 and 62 seconds
> long (up to 2 leap seconds can be added or removed), and having timers
> able to handle 25:59:60 as a valid date ?
The problem is NOT the 60 sec display. That is simply a translation from
the system time, which is in "seconds since". to something readable by
humans. The problem is system seconds. System seconds are in UTC
seconds, and that is discontinuous. Thus on Jun 30 23:59:59 system
seconds reads 1435733999 One second later utc reads 1435734000 .9
seconds later, it reads 1435734000.9 . 0.1 sec later it reads
Ie there are now two times at which utc seconds read 1435734000, It is
discontinuous. HOw does one handle this is the problem. Now Mill's
answer is to stop the clock for that second, but if the clock is read
during that time, the readings are incremented by some tiny amount.
Others is to smear out that time. The other one is to use tai seconds
which are not discontinuous but require translation to utc seconds
evertime they are used. UTC is still the world standard time. That is
does not comply with naive expectations as to how computer time should
run is for computer people to worry about :-)
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