On Mon, Oct 23, 2017 at 7:28 AM, John Sauter < [email protected]> wrote:
> On Sun, 2017-10-22 at 23:46 -0600, Warner Losh wrote: > > > > > > On Sun, Oct 22, 2017 at 11:02 PM, John Sauter <John_Sauter@systemeyes > > computerstore.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. > > > > By that logic, one should avoid any interval that includes June 30 or > December 31, since such an interval might include a leap second. Yes. That's the problem with leap seconds. Warner
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