[LEAPSECS] leap second roundup 2017

[Warner Losh]

On Sun, Oct 22, 2017 at 11:02 PM, John Sauter <
John_Sauter at systemeyescomputerstore.com> wrote:

> On Sun, 2017-10-22 at 17:53 -0700, Steve Allen wrote:
> >
> > The BIPM has contributed
> > CGPM draft Resolution "On the definition of Time-Scales"
> > For two years various meetings have indicated that a document like
> > this was under construction, so this is probably that result.
> >
> > A draft of the document seems to be at
> > http://www.iaufs.org/CCTF%20Recommendation-DRAFT.pdf
> > It largely seems to be a formal way for the CGPM to update the
> > definition of TAI and UTC to match what the IAU did over a decade
> > ago.
> > Unsurprisingly it makes no mention of the connection between the
> > calendar day and UT1.
>
> The next-to-last bullet point under "clarifies that" states that "UTC
> is also a means of dissemination of the standard of frequency; however
> this function is limited to intervals that do not contain leap
> seconds;".  Why the concern about leap seconds?  As long as you know
> the name of each second, why should it matter that there is a leap
> second in the interval?
>

Because one cannot reliably know that. And by reliably, I mean everybody
knows, all the software knows, all the software agrees, even among diverse
groups whose primary purpose may not be time keeping and may have sloppy
habits about leap seconds (eg, the real world).

One can know it, sure, but one cannot count on every single other person
who touches the data knowing it with certainty. So it's just best to avoid
data that spans a leap second.

Warner
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