Re: [LEAPSECS] Consensus rather than compromise

From: John.Cowan <>
Date: Wed, 31 Aug 2005 22:04:17 -0400

Mark Calabretta scripsit:

> Currently the timezone offset is essentially fixed for a particular
> place, yes there are quirks but it's hardly relevant to the argument.

If by "currently" you mean "at this very moment", then that's trivially
true. If by "currently" you mean "in the last few decades", then it's false.

Zoneinfo currently recognizes 365 distinct localities on the basis of
nationality or distinct history (since the Epoch, some 1125539538 seconds
ago) or both. Of these, only 129 have had a fixed offset since the
beginning of LCT in that locality. And of those, 55 have changed their
DST rules at least once, leaving only 74 that have been entirely stable.

> Under the proposed scheme, timezone offsets would be a function of epoch
> as well as place, thus requiring another table for each timezone.

This is already the case: nothing new is needed.

> However, there would be a fundamental difference between the DST and TZ
> rules: the former are quantized at 0 or +1, so you can only ever get it
> wrong by one hour. However, the TZ offset would not be limited in
> range, over millenia it would span many hours, one hour in the first
> millenium and accelerating.

Eastern Kiribati has already changed from UTC-10 to UTC+14, a 24-hour
discrepancy. It'll be a long time before any rotationally induced
offset changes will amount to that.

Eventually, of course, it'll be impossible to maintain the fiction
that the Earth rotates in anything like 24 hours. IIRC the maximum
possible slowing before the Earth becomes tidally locked to the Moon
is 47 current days; when an "hour" lasts almost two sleep-wake
cycles, the current clock will *have* to be revised.

> John Cowan argues that timezones will tend to coalesce as nations reach
> agreement, but remember that we are talking about timescales of
> millenia. Over such times nations as a whole don't tend to reach
> agreement - consider how the Gregorian calendar was adopted piecemeal by
> different countries (empires really) over centuries.

A process which is now essentially complete, however. A few countries
still use other calendars officially, but the Gregorian calendar is
well-known there anyhow. No novel calendar has been adopted anywhere
since 1583.

> But the killer is that a timezone only needs to fragment *once* in order
> to require the creation of a separate TZ rule table.

Quite so, but what of it? People who do not care about LCT in the new
locations can ignore the table update; those who do care have a strong
incentive to download the new tables. Systems that need not worry about
LCT, need not care at all.

While staying with the Asonu, I met a man from      John Cowan
the Candensian plane, which is very much like
ours, only more of it consists of Toronto.
        --Ursula K. Le Guin, Changing Planes
Received on Wed Aug 31 2005 - 19:05:47 PDT

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