[time-nuts] LSEM (Leap Second Every Month)

Michael Rothwell michael at rothwell.us
Thu Jul 21 23:35:12 EDT 2016


On Thursday, July 21, 2016, Michael Wouters <michaeljwouters at gmail.com>
wrote:

> Apropos Bob's comments, the problem of ambiguous timestamps during a
> leap second, at least with current operating systems, is only made
> worse by more frequent leap seconds.
>
> Making critical systems run on a leap second free time scale like TAI,
> for example, just shifts the problem to the interface between those
> systems and the rest of the world. Admittedly, this interface may be
> more tolerant of discrepancies.
>
> Leap seconds have gotta go.


No leap seconds seems preferable to more frequent leap  seconds.


>
> Cheers
> Michael
>
>
> On Fri, Jul 22, 2016 at 8:13 AM, Bob Stewart <bob at evoria.net
> <javascript:;>> wrote:
> > But would it really solve your problems, Jim?  The problem is
> essentially that periodically, there are two different clock times that
> represent the same moment in time.  For telescopes, stock markets, spread
> spectrum, time-based encryption, etc that's a big problem.  Would it not be
> better to separate out those entities that are more dependent on precision
> sequence than on clock time and accept that they are just going to be
> different?  Yeah, the talking heads on CNBC and Bloomberg would gravely
> announce that today's stock market was opening a second later, but so
> what?  At least there wouldn't be any more questions about exactly when
> transaction X occurred.
> >
> > Bob
> >  -----------------------------------------------------------------
> > AE6RV.com
> >
> > GFS GPSDO list:
> > groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> >
> >       From: Jim Palfreyman <jim77742 at gmail.com <javascript:;>>
> >  To: Discussion of precise time and frequency measurement <
> time-nuts at febo.com <javascript:;>>
> >  Sent: Thursday, July 21, 2016 4:38 PM
> >  Subject: Re: [time-nuts] LSEM (Leap Second Every Month)
> >
> > The idea is the same as my local telco and their main exchanges.
> >
> > Every month they walk up to the main circuit breaker and cut the power to
> > the entire building. All the UPSs and diesel generators get tested in
> anger.
> >
> > This leap second solution is the best I've heard so far.
> >
> > Personally I now hate leap seconds because it ruins many hours of my
> > observations at the radio telescope - but if this was implemented it
> would
> > force the software problems to be fixed.
> >
> >
> > Jim Palfreyman
> >
> >
> > On 22 July 2016 at 06:01, Brooke Clarke <brooke at pacific.net
> <javascript:;>> wrote:
> >
> >> Hi Tom:
> >>
> >> I like this idea.  I addresses the lesson from Y2K that something done
> >> often works much better than something done only occasionally.
> >> That's way you see the firetruck at the local store, because it's used
> all
> >> the time and so is more likely to work when needed.
> >>
> >> --
> >> Have Fun,
> >>
> >> Brooke Clarke
> >> http://www.PRC68.com
> >> http://www.end2partygovernment.com/2012Issues.html
> >> The lesser of evils is still evil.
> >>
> >> -------- Original Message --------
> >>
> >>> Hi Tom...
> >>>
> >>> Does your proposal allow for a Zero leap second, or does it require
> >>> either plus or minus 1 to work? Seems like you could stay closer to the
> >>> true value if you also have a zero option. Might also cause less
> >>> consternation for some services, like the finance and scientific
> worlds,
> >>> that seem to have critical issues when an LS appears.
> >>>
> >>> I like your point that by having it occur monthly it forces systems to
> >>> address issues promptly, and maybe that's the argument for the non-zero
> >>> option.
> >>>
> >>> Tom Holmes, N8ZM
> >>>
> >>>
> >>> -----Original Message-----
> >>> From: time-nuts [mailto:time-nuts-bounces at febo.com <javascript:;>] On
> Behalf Of Tom Van
> >>> Baak
> >>> Sent: Thursday, July 21, 2016 1:28 PM
> >>> To: Discussion of precise time and frequency measurement <
> >>> time-nuts at febo.com <javascript:;>>
> >>> Cc: Leap Second Discussion List <leapsecs at leapsecond.com
> <javascript:;>>
> >>> Subject: Re: [time-nuts] Leap second to be introduced at midnight UTC
> >>> December 31 this year
> >>>
> >>> Time to mention this again...
> >>>
> >>> If we adopted the LSEM (Leap Second Every Month) model then none of
> this
> >>> would be a problem. The idea is not to decide *if* there will be leap
> >>> second, but to force every month to have a leap second. The IERS
> decision
> >>> is then what the *sign* of the leap second should be this month.
> >>>
> >>> Note this would keep |DUT1| < 1 s as now. UT1 would stay in sync with
> >>> UTC, not so much by rare steps but by dithering. There would be no
> change
> >>> to UTC or timing infrastructure because the definition of UTC already
> >>> allows for positive or negative leap seconds in any given month.
> >>>
> >>> Every UTC-aware device would 1) know how to reliably insert or delete a
> >>> leap second, because bugs would be found by developers within a month
> or
> >>> two, not by end-users years or decades in the future, and 2) every
> >>> UTC-aware device would have an often tested direct or indirect path to
> IERS
> >>> to know what the sign of the leap second will be for the current month.
> >>>
> >>> The leap second would then become a normal part of UTC, a regular
> monthly
> >>> event, instead of a rare, newsworthy exception. None of the weird bugs
> we
> >>> continue to see year after year in leap second handling by NTP and
> OS's and
> >>> GPS receiver firmware would occur.
> >>>
> >>> Historical leap second tables would consist of little more than 12 bits
> >>> per year.
> >>>
> >>> Moreover, in the next decade or two or three, if we slide into an era
> >>> where average earth rotation slows from 86400.1 to 86400.0 to 86399.9
> >>> seconds a day, there will be zero impact if LSEM is already in place.
> >>>
> >>> /tvb
> >>>
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-- 
Michael Rothwell
michael at rothwell.us
(828) 649-ROTH


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