On -10.01.-28163 20:59, Miroslav Lichvar wrote: > On Mon, Jun 23, 2014 at 11:45:16PM -0500, Mike S wrote: >> On 6/16/2014 6:05 AM, Jochen Bern wrote: >>> There are four official slots - two primary, two secondary - over the >>> course of the year to insert leap seconds, >> Those are only preferences. Leap seconds may be inserted at any month >> boundary.
I'm positive that I've *seen* ntpd do the poll-interval-reduce on a *quarterly* base a couple years back. As Miroslav mentioned, the IERS - the guys who *schedule* leap seconds - currently *use* only the primaries, while still *mentioning* the secondaries as well: "Leap seconds can be introduced in UTC at the end of the months of December or June, depending on the evolution of UT1-TAI. [...] According to the CCIR Recommendation, first preference is given to the opportunities at the end of December and June, and second preference to those at the end of March and September." -- http://www.iers.org/nn_10828/IERS/EN/Publications/Bulletins/directLinks/bulletin__C__MD.html Of course the number of leap seconds required in recent years helped sticking with only the primaries, so it's a bit unclear to me which of all those choices are "for the moment" and which are long-term ... > Sooner or later, not even 12 leap seconds per year will be enough to > keep UTC close to UT1. Hopefully they will be abolished long before > that. I do not wish to see that day, regardless of whether you're referring to a couple millennia of Earth-Moon tide-locking or a major off-center impact giving the crust a new spin. :-S > Practically speaking, beside having to make more than two corrections > per year (which is not expected to happen in the next few decades), > could there be any reason to do it in other months than June and > December? I've browsed the results of the infamous poll and most of the people voting "abolish leap seconds" apparently didn't mean to actually *abolish* them (as in, decouple UT1 and UTC, or whatever their successors might be called), but to have them *rearranged* into fewer and larger leaps. Of course, one can imagine that to go the other way - i.e., smaller but more frequent leaps. In general, I consider the entire procedure to first and foremost reflect a couple *external* facts - namely, a) the time necessary to propagate the decision on leap [whatever] scheduling to wherever it has to be carried out (NTP is *not* the critical path there, I'd guess) and b) the (ever-improving) quality of *prediction* of Earth's rotation. If those two restrictions were to be removed (assume a giant tooth fairy if you must ;-), I don't see a reason why the current UT1-UTC delta could not be communicated through an "NTP-ng" in the same way today's NTP shoves server-client deltas around and corrects for them - piecemeal with every poll. (Returning to your question as phrased, and circumstances as of today: IIUC the quality of prediction *would* already suffice to attempt scheduling leap seconds so as to aim for min-sum-of-squares, rather than predefined schedule slots.) Regards, J. Bern -- *NEU* - NEC IT-Infrastruktur-Produkte im <http://www.linworks-shop.de/>: Server--Storage--Virtualisierung--Management SW--Passion for Performance Jochen Bern, Systemingenieur --- LINworks GmbH <http://www.LINworks.de/> Postfach 100121, 64201 Darmstadt | Robert-Koch-Str. 9, 64331 Weiterstadt PGP (1024D/4096g) FP = D18B 41B1 16C0 11BA 7F8C DCF7 E1D5 FAF4 444E 1C27 Tel. +49 6151 9067-231, Zentr. -0, Fax -299 - Amtsg. Darmstadt HRB 85202 Unternehmenssitz Weiterstadt, Geschäftsführer Metin Dogan, Oliver Michel _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
