On Mon, 2016-04-11 at 11:10 -0700, Steve Allen wrote: > On Mon 2016-04-11T10:17:33 -0400, John Sauter hath writ: > > > > Using ancient observations of the Sun and Moon, construct a time > > scale > > using the modern definition of Coordinated Universal Time to cover > > the > > past 3,000 years. Use the 20th century portion of that time scale > > to > > construct a table of leap seconds from 1900 through 1971 for NTP. > I find this to be akin to offering an answer to this question: > What is the arcsine of -2? > > While there may be some applications which need that sort of answer, > in general it is important to recognize that prior to 1972-01-01 > there > were no civil applications making use of SI seconds. Every practical > application before 1955 was using mean solar seconds. > > A time scale based on SI seconds extended back to 1900 does not > correspond to any contemporary use. The nature of time scales in > actual use over history is necessarily piecewise continuous. > Applications should be aware of that and make a choice about whether > they want conceptual simplicity or a particular kind of technical > accuracy. In general it is better for the characteristics of the > time > scale to be driven by the needs of the application rather than > supplied in the absence of particular requirements. > > So this is cool, and may be applicable to some applications, but I'm > not sure which ones those are. > > -- > Steve Allen <s...@ucolick.org> WGS-84 > (GPS) > UCO/Lick Observatory--ISB Natural Sciences II, Room > 165 Lat +36.99855 > 1156 High Street Voice: +1 831 459 3046 Lng > -122.06015 > Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 > m
Thanks for taking the time to read the article, Steve. You are, of course, correct that the choice of time scale needs to be driven by the needs of the application. As you hint, this is a solution looking for a problem. It is my hope that by publishing the article perhaps it can find a problem. The application I have in mind is similar to Mayan scholars who write for a general audience, and use proleptic Gregorian so they can express dates in a familiar form. Perhaps there is an application that wishes to describe times that are precise to the second, but are a thousand years ago. John Sauter (john_sau...@systemeyescomputerstore.com) -- PGP fingerprint = E24A D25B E5FE 4914 A603 49EC 7030 3EA1 9A0B 511E
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