Re: [Ntp] Leap second

[Martin Burnicki <[e-mail]>]

Rob,

Seaman, Robert Lewis - (rseaman) wrote:
> Just a reminder that UTC does not have repeated seconds, whatever
> POSIX says, or NTP implements. Seconds are interposed (or elided) as
> needed. UTC second number 61 in that minute is distinct from second
> number 60. Or second number 59 of one minute is immediately followed
> by second number 1 of the next. If you want different behavior,
> define or adopt a different time scale.
The problem is that operating systems don't know anything about seconds
numbered 60 or 61 since they only count seconds since an epoch, and some
runtime library has to convert it to calendar date and time.

Even if the number of the second since an epoch is repeated when a leap
second is inserted, it would not be a big problem if the system calls
commonly used to retrieve the system time would provide an associated
status.

If you read the time from a Meinberg PCI card in a fast loop across an
inserted leap second the you can also evaluate a status that indicates
which second is the inserted second, so conversion function can return a
second number 61 for that second.

A similar call which returns the current time plus the kernel time
status is also available on most Unix-like systems, but applications
normally don't use it because it takes longer to execute.


Martin
-- 
Martin Burnicki

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