[LEAPSECS] it's WP7A week in Geneva

M. Warner Losh imp at bsdimp.com
Mon Oct 5 22:33:51 EDT 2009

In message: <1EBBF6BD136D4B7AA983517FC850ED93 at grendel>
"Gerard Ashton" <ashtongj at comcast.net> writes:

: I find it remarkable that one group of time users chose a

: particular time dissemination mode (GPS) and made the typical

: array of poor decisions / errors with software. They also

: create a rather arbitrary demand of obtaining correct UTC

: within 5 minutes of installing hardware that has been

: sitting on a shelf for years.

Keep in mind that the people that wanted the solution, and the people
that implemented them were two different sets of people.

: They then decide the solution to there largely self-made

: problems is that the rest of the world should:

: -Redefine the name for the most widely used time scale in a way that conflicts

: with the present definition.

The problem exists independent of GPS. GPS is just the best way to
demonstrate the problem. The basic problem is that UTC is an
irregular system (sorry, has a variable radix, which is the same thing
from a software point of view). Experience has shown that the
disconnect causes problems.

: -Everyone who wrote correct software to re-correct the software.

Actually it depends on what you define as correct. Everybody that
implements leap seconds in time keeping will automatically be correct
if they were eliminated. It would still work if leap seconds were
scheduled out more than 6 months in advance too.

People that wrote code assuming DUT1 < 1s could be argued to not be
correct. They are merely close to correct. It bounds the error. A
more correct program would accept better corrections. Many telescopes
already download better estimates from the web and would be unaffected
either by their elimination or their scheduling (although their
elimination would eventually overflow fixed width formats in some
sources of DUT1).

: -Abandon any cultural connection between civil time and actual

: earth rotation

The railroads already did that 150 years ago when standard time was
adopted. Most people live their lives where the sun has an apparent
error of tens or hundreds of minutes off. This poses no problem to
people at all. This suggests that UTC's DUT1 requirement likely could
be relaxed without any major cultual damage.

We're also putting off the problem. Given the quadratic acceleration
of drift, one day we'll have to have a better system is
synchronization to the earth's rotation is to remain viable.

: -Rewrite laws that refer to mean time so they refer to UTC, since the

: difference between mean time and UTC will gradually become legally

: significant.

Actually, the laws that refer to UTC are fine. If the UTC definition
is tweaked, they are still valid. It is the ones that refer to mean
solar time that are problematical.

: I'm inclined to reject the proposal on the grounds that the proposers are

: too arrogant.

Since your arguments are overstated, maybe your conclusion is too.

Keep in mind that there are many proposals that have been circulated
and the tone of your post is highly arrogant in that it ignores the
others and is mostly an emotional reaction. The earth has shown
itself to be an unreliable time keeper, and the current system is
showing signs of strain...


: Gerry Ashton



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