Re: [LEAPSECS] building consensus

From: Zefram <zefram_at_FYSH.ORG>
Date: Mon, 5 Jun 2006 18:15:23 +0100

Warner Losh wrote:
>There's a reference to a book
>which is good.

This book needs to be treated with caution. (It's like news outlets:
they get wrong the things one has specialised knowledge of; extrapolate to
what one doesn't know about.) Its conversion algorithms are numerically
correct as far as I can tell, but the correct interpretation of the
inputs and outputs is not always as stated. The code is of very limited
use anyway due to a restrictive licence.

The conceptual description of what's going on is often muddled. There are
no fewer than three different forms of their "RD" dating system (integer
identifying local noon; integer identifying local midnight-to-midnight;
fractional taking integer values at local midnight), and they never make
explicit which one they are using. The book has no concept of timezones,
and so mixes up absolute dating systems with timezone-relative ones.
And so on.

The errata list (on their website) is a must for anyone reading the book.
I advise not actually accepting any factual material from the book at all:
use it only for hints, and accept only what you can derive yourself.

>>> However, in 1704 something went wrong and the plan was not carried through;
>>> they did, after all, have a leap year that year. And one in 1708. In 1712
>>> they gave it up and went back to Julian, putting 30 days in February that
>>> year!...

I had that case in mind for the concept of "calendar zone". Similarly the
Roman civil calendar from -44 to 8 CE, which was not actually the true
Julian calendar due to faulty operation of the leap year rule.

Received on Mon Jun 05 2006 - 10:15:44 PDT

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