Re: [LEAPSECS] interoperability

From: Rob Seaman <seaman_at_NOAO.EDU>
Date: Mon, 9 Jan 2006 09:41:40 -0700

On Jan 9, 2006, at 12:23 AM, John Cowan wrote:

> 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.

Communication prospers when people's clear meaning is not subjugated
to petty grammarians.

We are now - and have been - discussing timekeeping changes that call
into question the definition of a "day". Those of us who support
solar time are fundamentally asserting the primacy of the the
standard day over the standard second (for civil timekeeping
purposes). Those of us who consider solar time to be a curious
anachronism, assert the the SI second over the concept of a day (for
civil timekeeping purposes).

> 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.

At the risk of igniting a new round of "stage two" nonsense, consider
the implications of your statement. Currently LCT (as you appear to
mean it) is standard time. Daylight saving (under whatever name) is
merely an overlay on standard time. Standard time has no jumps
(except for leap seconds).

Under your suggestion, LCT would include the jumps for daylight
saving time (if locally used) as well as the jumps to correct for the
cumulative effect of tidal slowing. As I hope I have established,
these are "fall back" discontinuities that would result in the same
hour of LCT occurring twice. Is this not perceived to be a problem?

Rob
Received on Mon Jan 09 2006 - 08:42:37 PST