Re: [LEAPSECS] LOD reaches 0 s/d
On Thu, Nov 12, 2020 at 5:24 PM jimlux 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 ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LOD reaches 0 s/d
On Thu, Nov 12, 2020 at 4:46 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 ? > I'd poke my hand up, but when I tested it, it severed my arm... Warner ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LOD reaches 0 s/d
On Thu, 12 Nov 2020 23:45:52 +, 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 ? Twenty years ago, I tested a very large radar for the general effect of a leap second by arbitrarily causing the local clock by one second, in both directions. Radar software gyrated and settled down on the inserted leap second, and really gyrated on a deleted second. But nothing failed. This tests mostly the radar tracking software, and not leap second handling per se. The radar passed - the momentary gyration was not a problem in practice. Joe Gwinn ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LOD reaches 0 s/d
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. ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] LOD reaches 0 s/d
> 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 ? -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
[LEAPSECS] LOD reaches 0 s/d
The latest Bulletin A [https://datacenter.iers.org/data/latestVersion/6_BULLETIN_A_V2013_016.txt] 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. Michael Deckers. ___ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
