Date: Wed, 04 Jan 2006 01:24:27 +0100 From: Carlos Amengual <listas@informatica.info> To: John-Mark Gurney <gurney_j@resnet.uoregon.edu> Cc: freebsd-current@freebsd.org Subject: Re: FreeBSD handles leapsecond correctly Message-ID: <43BB15BB.2070705@informatica.info> In-Reply-To: <20060103234638.GA69162@funkthat.com> References: <20060103120026.EEEC916A41F@hub.freebsd.org> <43BAE883.1090705@informatica.info> <20060103234638.GA69162@funkthat.com>
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John-Mark Gurney wrote: > > Having talked with a sextant user... leap seconds don't matter to > sextant users... They have a book of times and possitions, and the > book is only good for a year or two... so needs to be reprinted, and > on reprints, they can take care of the leap second issue... Those tables are valid for a year (you can use computer programs too). If you use software, you have to fix the software, and if you use tables then a new set of tables has to be produced, where the time argument is not Universal Time (as until now), but Dynamical Time (TDT), or maybe something in the middle: "Dynamical Time plus something". > so, the only fix for a sextant is a new table of numbers... don't > forget the tables HAVE to be updated for precisely the reason leap > seconds are inserted... It is not only an update, it is a change in the tables themselves. And sidereal time would no longer be sidereal time. The current nautical tables use UT and not TDT as time argument precisely to avoid confusing people with timescales. Astronomical tables already use TDT (except for sidereal time), which is the kind of timescale that you want (TDT is based on TAI). Regards, Carlos Amengual
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