Re: [LEAPSECS] Mechanism to provide tai-utc.dat locally

From: Rob Seaman <seaman_at_noao.edu>
Date: Fri, 29 Dec 2006 02:49:52 -0700

Tony Finch wrote:

> You need to do so in order to implement an accurate clock, since
> the clock produces interval time and you need a way to convert its
> output to time of day.

As Steve Allen has pointed out, it is in the nature of a clock to be
reset on occasion. What is NTP but a mechanism for managing these
resets? What is any clock discipline? What else does it mean to
maintain "traceability"? What is a change in rate, but a reset
schedule carried to a limit? (Although Steve might replace "reset"
with "maintain a list of offsets".)

I don't disagree that maintaining updated access to a master list of
resets (leaps) or rate changes provides one avenue to "implementing
an accurate clock", i.e., "synchronizing one clock to another". But
even today this often is, can be, will be, managed by resetting one
clock as needed, manually if necessary. And even with a detailed
long range list of leaps in hand, there is still a responsibility to
implement each leap correctly as a 61s or 59s minute. Otherwise this
6 month or 10 year or 600 year lookahead is no better than having
Harold Lloyd reset your clocks by hand.

One might also point out that the clocks in most PCs are far less
even tempered than Madre Tierra. I don't suppose anybody has thought
to run the various DUT1 possibilities past the NTP v4 working group?
One could do worse than to adopt the NTP clock discipline writ large
as a baseline leap second scheduling algorithm. As discussed
recently, there is a natural scale to the tempering of DUT1. Working
with that, rather than with some arbitrary "forget the whole thing"
strategy, is likelier to converge on consensus.

And just to stay on message, let me point out that nothing in the so-
called leap hour proposal covers any of these issues. The only way
to create a new workable consensus on civil timekeeping is to address
the key issues forthrightly.

>> This is a static offset.
>
> No, it is subject to arbitrary political variations.

Evidently.

However, "whimsically redefined" is not the same as "changing in a
secular fashion".

Rob
Received on Fri Dec 29 2006 - 01:50:06 PST