Re: [LEAPSECS] Consensus rather than compromise

From: Mark Calabretta <mcalabre_at_atnf.CSIRO.AU>
Date: Fri, 02 Sep 2005 14:34:46 +1000

On Thu 2005/09/01 10:46:57 -0400, "John.Cowan" wrote
in a message to: LEAPSECS_at_ROM.USNO.NAVY.MIL

>(N.B. The 1896 shift is *not* the reason Broken Hill is separated
>from Sydney, since that event took place before the Epoch. Rather,
>it is because Broken Hill adopted Adelaide's DST rules in 2001.)

zoneinfo's fragmentation, the Broken Hill (Yankowinna) effect if you
like, already illustrates the second part of my argument. Also, as
Rob Seaman points out, the very fact that these half-hour zones exist
suggests that a half-an-hour difference in solar time matters very much
to some.

>I have done some work on the zoneinfo source data to generate a three-
>column table summarizing the changes in the world's 365 time zones.
>The table can be downloaded from .

Thanks for the list, I freely admit that there are many more recent
changes than I had expected, though I think the fragmentation effect
tends to magnify the number. For my purposes filtering the list as

   awk '{print $1, $2}' zone-changes.txt | sort -u

produces something closer to what I had in mind, but it would be useful
to have dates associated with these entries - many would come from the
first few decades of the 1900s when the time zones were settling into

However, it still doesn't affect the first part of my argument. To
understand why, imagine the typical timezone map such as that at, or at the front of any decent
atlas, but colour-coded so that red at +12 grades through the rainbow
to violet at -12. Now imagine a movie of how that map has changed over
time as described by zoneinfo. In your mind's eye you should see that
the map basically stays the same but with a degree of jitter in the
boundaries either to the east or west by up to an hour or so, which
essentially amounts to permanent daylight savings being enabled or
disabled. (BTW, that also applies to Kiribati with the date line.)
Mistaking the time zone should not produce errors of more than an hour

Now imagine how the map would change if leap hours were introduced; you
should notice two things, firstly a secular change such that each place
on the map becomes progressively redder, and secondly a progressive
fragmentation of the boundaries as each administration decides
independently what to do with the leap hour.

Mark Calabretta
Received on Thu Sep 01 2005 - 21:36:20 PDT

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