Re: [LEAPSECS] A lurker surfaces

From: Rob Seaman <seaman_at_noao.edu>
Date: Sat, 30 Dec 2006 20:42:28 -0700

Jim Palfreyman wrote:

> With my time hat on, having time that is discontinuous pains me. It
> doesn't make sense "in my heart". But at least these
> discontinuities are in whole seconds.
>
> Any discontinuities must be regularly done. So they are part of all
> computer systems and are tested and used all the time. Don't let
> them build for a decade - that is bad bad news.

Just a reminder that UTC has no - none - nada - discontinuities.
Various computer mis-implementations may, but the standard is very
carefully constructed to avoid spring-forward or fall-back gaps or do-
overs.

This is just one of many flaws of the notion of leap hours. A leap
hour (like a leap second or leap day) is an extra intercalary
temporal unit inserted into the continuous flow of time. A leap hour
is NOT an unmatched fall back do-over - the day in question would
have 25 regular, ordinary, permanent, unique hours - and the extra
hour would occur contemporaneously worldwide. It would not involve
an easy floating 2 am Sunday local clock reset.

So, for example, if the leap hour is 2606-12-31, 24:00:00 to 24:59:59
UT, it would fall BETWEEN 18:59:59 and 19:00:00 EST, just like a leap
second today is 23:59:60 UT or 18:59:60 EST, also falling between
18:59:59 and 19:00:00. In each time zone in turn, the leap hour
would fall between different otherwise sequential clock ticks - a non-
issue with a leap second, not so easy to ignore with a leap hour.
Still not a discontinuity, but certainly a real pain for anyone who
is trying to keep the events of the day straight.

More than likely, the hour would be labeled the same worldwide, so
the EST clock would run 18:59:58, 18:59:59, 24:00:00, 24:00:01, ...,
24:59:58, 24:59:59, 19:00:00, 19:00:01, ...

Rob
Received on Sun Dec 31 2006 - 00:50:33 PST