Re: [LEAPSECS] what time is it, legally?

From: Rob Seaman <seaman_at_noao.edu>
Date: Tue, 12 Dec 2006 11:22:01 -0700

On Dec 12, 2006, at 9:38 AM, Zefram wrote:

...a lot of stuff I agree with.

> Standard timezones have replaced solar time in general use

But this needs a clarification. Standard time replaced local
apparent solar time in several steps. First, clock (mean) time
replaced apparent time for civil purposes. As you can see from the
proliferation of railroad standards, these were both still local to
one place or another. Later, local time was referenced to standard
localities such as Greenwich. Still later, a loose international
consensus was formed regarding a common time zone system with a
single standard prime meridian.

All of these remained solar time. Mean solar time of some remote
location is still a flavor of solar time because there is no secular
drift. The important issue is the continuity of still recognizing
mean solar time as the foundation of civil time. Leap seconds are
simply one possible mechanism for achieving this. The notion of a
leap hour fails to preserve mean solar time in any practical fashion.

Rob Seaman
NOAO
Received on Tue Dec 12 2006 - 10:22:45 PST