Re: [Ntp] Leap second draft

[Steve Allen <[e-mail]>]

On Sat 2019-03-30T09:42:38-0600 Warner Losh hath writ:
> We definitely need that it was exactly 10s in 1972, as opposed to 0. And we
> need statements that things were messy before 1972. This information is
> 'out there' but hard to find and difficult to properly interpret.

Due to ongoing activities like the CGPM meeting last November
specifying things like "9,192,631,770" become obsolete in less than 8
weeks.  For the same reason saying that TAI is like TT risks
obsolescence because of changes in the notion of the geoid, or the
standard geopotential, or some other tweak to the external definition
like the ones that have been made by one or more of IAG, IAU, or CGPM.

The lifetime of an IETF document may be improved by limiting the
amount of reiteration.  Do describe the important and presumed
unchanging properties of the external definition so that if changes
happen in the future the readers can make a judgement about whether to
abandon the existing implementation or ignore the new external
definition.  Then rely on simply citing which external agencies are in
charge of external definitions that are being used by NTP.

Unfortunately for this origins of this subject matter the principals
who were involved with the inception of leap seconds were not happy
with the result.  The contributions to the CCDS meeting of 1972 show
they had decided not to use UTC with leap seconds in their own
systems, they believed that others would be best doing likewise, and
they agreed not to talk about it outside of the folks who had been at
the meetings which resulted in leap seconds.  Their silence left the
story to be told without explanation of reasons and motivations; thus
it became hard to find and interpret.

--
Steve Allen                    <[e-mail]>              WGS-84 (GPS)
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