On Wed, 2016-04-13 at 00:37 +0100, Zefram wrote: > John Sauter wrote: > > > > https://www.systemeyescomputerstore.com/proleptic_UTC.pdf. > Your abstract says you provide a leap schedule for 1900 to 1971, but > actually you provide a leap schedule for -1000 to 1971. The abstract > seems to suggest some distinction in objective between what is done > for > the 20th century and for the preceding 2900 years, aiming to "cover" > the latter but "construct a table of leap seconds" for the former, a > distinction that doesn't seem to make sense and doesn't actually > exist > in the paper. (You do give the leap table in a second format for the > 20th century portion, but in substance this is only duplicating part > of > the table earlier in the paper.) > > Your proleptic leap schedule generally looks sane. I haven't checked > the numbers in detail. It is good to incorporate Tony Finch's pUTC, > as > you do. Where more than 12 leaps are required in a year, your > extension > to leaping on the 15th day of a month is sensible. > > Your delta-T table confuses points in time with the intervals between > them. The delta-T column itself applies to (the start of?) the > specific > year listed, but the "change in delta-T" and "seconds per year" > columns > apply to the interval between the year listed on that line and the > year > listed on the following line. > > The column labelling for that table, and its accompanying text, isn't > great. You should state what delta-T means, address units, and > generally > make clearer what the table means. > > You write generally as if UTC exists only for 1972 onwards. You > should > acknowledge the existence of the former (1961 to 1971) rubber-seconds > UTC, and make clear that your schedule is not a proleptic extension > of > the whole of UTC but only of the leap-seconds form of UTC. > > Your NTP material is mostly a mistake. For NTP's purpose of clock > synchronisation, it needs to know about contemporary leap seconds, > but > has no need for knowledge of historical leap seconds. There is > therefore > no value, for this purpose, in extending the historical leap schedule > further back. It is entirely erroneous to suppose that this paper > has > any bearing on NTP, and I see no value in the paper mentioning NTP. > Some of the specific things you say about NTP are in error, but I > won't > go into detail due to this overriding concern. > > You should address the question, currently ignored, of what time > scale > your proleptic UTC is based on. If your aim is to fully construct > a time scale, this is a necessary component. Actual UTC, both of > the leap-seconds form and the rubber-seconds form, is defined as > a transformation of TAI. TAI is only defined back to some time in > 1955, because it is defined by the actual operation of atomic clocks. > This covers Finch's pUTC, but you go far further back, millennia > before > there are any atomic clocks. The delta-T figures that you used are, > strictly, referenced to TT. To construct a usable time scale you'll > need > to use something close to TT as the basis, and manage the transition > between your proleptic basis time scale and the real TAI-based UTC. > I'd be inclined to use the basis TAI(TT) = TT - 32.184 s prior to > 1977, > switching to TAI at 1977-01-01T00:00:00 TAI when by definition > TAI(TT) > = TAI, though this does mean using a different basis from the real > UTC > for five years of real leap-seconds-UTC history. > > It would be helpful for you to provide a distinctive name for the > time > scale that you construct. "Proleptic UTC" is a reasonable > description, > but not sufficiently specific to use as a name. > > -zefram > _______________________________________________ > LEAPSECS mailing list > [email protected] > https://pairlist6.pair.net/mailman/listinfo/leapsecs
Thank you for your detailed criticism, Zefram. I will think about what you have said and revise the article. John Sauter ([email protected]) -- PGP fingerprint = E24A D25B E5FE 4914 A603 49EC 7030 3EA1 9A0B 511E
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