[LEAPSECS] LOD reaches 0 s/d

[Warner Losh]

On Thu, Nov 12, 2020 at 5:24 PM jimlux <jimlux at earthlink.net> wrote:

> On 11/12/20 3:45 PM, Poul-Henning Kamp wrote:
> > --------
> >
> >>      predicts that d(UT2)/d(TAI) = 1 after 2021-11-13, ie
> >>      the rates of UTT2 and TAI are expected to agree for the
> >>      next year. This has never happened since 1961. We may
> >>      not need to abolish leap seconds for quite a while.
> >
> > Unless of course we get close enough to a negative one, that people
> > are *really* going to freak out.
> >
> > Hands in the air:  Who here besides Warner and me has ever tried to
> > test handling of negative leap-seconds ?
> >
>
> not exactly leap seconds, but I had a system that ingested time from two
> sources that were nominally synced, and one slipped behind -  it was a
> gruesome disaster. Time going backwards creates ALL sorts of problems
> with log files and locking schemes and telemetry decoding/plotting that
> assume that time is monotonically increasing. (we leave, aside, the
> whole daylight time issue - that's a "print formatting of time values"
> thing.
>
>
> It fills me with great trepidation if clock time were ever to go
> backwards.  I think what would happen is that people would hack it and
> have it sort of run slowly over some seconds, while maintaining
> monotonicity.  And then create tiger teams to fix it when someone else
> did it differently, and your financial system ingested transactions that
> appeared to end before they started.
>

Well, every positive leap second is time going backwards...  At least with
a negative leap second time just skips a beat...

Warner
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