Re: [LEAPSECS] interoperability

From: John Cowan <cowan_at_CCIL.ORG>
Date: Mon, 9 Jan 2006 02:23:14 -0500

Rob Seaman scripsit:

> >Sure, and you can timestamp then on either timescale, because there
> >is a 1 to 1 translation between the two timescales [1].
> Perhaps I miss your meaning here, too. The event of migrating a time
> zone is a discontinuity just as with a leap second or leap hour.

Sure. But discontinuities in LCTs are something we already know how to handle.

> This is true. It is irrelevant to the underlying international
> clock.

PHK and I are denying any need for an international clock that tracks
Earth rotation.

> What matters is not when sunrise occurs, but rather that every day
> has one (and only one).

This is like the "day is light and night is dark" statement: there is,
at any given location, one and only one sunrise per (solar) day,
no matter what clocks say.

> Exactly. The pressures to maintain a common international vision of
> time will trump local variations. It is the resulting common
> international time clock that you won't let me refer to as "civil
> time". All requirements placed on UTC flow backwards from here. You
> can't just edit UTC (or GMT) out of the debate.

What common international vision of time? There is no common international

> stage one is atomic time (e.g., TAI)
> stage two is international civil time (e.g., UTC)
> stage three is local legal time (e.g., Mountain Standard Time)

What we are looking for is to redefine stage three directly in terms of
stage one without regard to a factitious stage two.

> >In a couple of hundred years, the Danish Parliament (or its
> >successor in interest) will simply decide "from YYYY-MM-DD HH:00,
> >the Danish Civil time will use offsets -3h and -2h (instead of
> >presently -1h/-2h) and the transition will happen on the switch
> >from summertime to wintertime by _not_ adjusting the clock".
> The only way this differs from the leap hour proposal is that you are
> assuming that different localities can (or would) carry these
> adjustments out separately.

Exactly! That is what the principle of subsidiarity demands, and it is
a situation we already know how to handle.

> A fall back event means that the clock (local, standard,
> international, whatever clock you want) first traverses an hour - and
> then traverses it again. Under the current three stage system it is
> only the most local stage three clocks that are affected. You are,
> in effect, promoting this discontinuity to stage two - to the
> worldwide business timescale. More to the point, you have said that
> stage one can be mapped back-and-forth to stage two. But we've just
> shown that this is no longer a one-to-one mapping since the hour is
> traversed twice, corresponding to two hours of TAI duration.

You've redefined stage two in the course of this discussion. Before it
meant LCT, now it means UTC. But be that as it may.

Since we (PHK and I) are in favor of abolishing stage two, we are not
promoting the discontinuity from stage three to stage two. Rather, we are
interested in allowing the various local authorities to introduce changes
into their stage three clocks *as they decide* to deal with any perceived

The "true leap hour" folks, if any, are actually doing what you say we are
doing: creating a large discontinuity in stage two. The "fake leap hour"
folks, if any, are actually doing what we want, but are cynically saying
there will be a leap hour in stage two while not expecting such a thing
to ever happen.

> Ah! But you've suggested that the other half of the annual daylight
> saving pendulum be used. This doesn't work because we're on the
> wrong side of the pendulum's arc. The point being that you don't
> need to *not* adjust the clock in the Autumn - you need to not adjust
> the clock in the Spring. It is the springtime "gap" in the mapping
> (also not a very desirable feature for a time scale) that is omitted
> during one of these events - not the harvest-time doubly traversed hour.

Fair enough.

> (We'll omit discussion of the fact that not all localities observe
> daylight saving time in the first place.)

By all means. (This is the rhetorical figure of *praeteritio*.)

> This is the same point I was trying to make about the 25 hour day.
> No historian or lawyer is going to look favorably on a situation that
> results in ambiguous timestamps. Perhaps, you say, such timestamps
> should all be kept in TAI. But in that case, we are back to the
> original question of why a stage two clock is needed at all. By
> asserting stage two is needed, all the rest logically follows.

And we assert that stage two is *not* needed. In any case, most of the
world's population deals with ambiguous timestamps every year.

As I've pointed out before, future times in legal documents are defined
as LCT for a particular place, since the future mapping between LCT and any
other time scale is not known. This turns out not to be a big problem,
except for the makers of calendar programs.

John Cowan
Be yourself.  Especially do not feign a working knowledge of RDF where
no such knowledge exists.  Neither be cynical about RELAX NG; for in
the face of all aridity and disenchantment in the world of markup,
James Clark is as perennial as the grass.  --DeXiderata, Sean McGrath
Received on Sun Jan 08 2006 - 23:23:32 PST

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