[LEAPSECS] June 30 not leap

[Steve Allen]

On Tue 2013-07-02T09:12:02 -0600, Warner Losh hath writ:

> On Jul 2, 2013, at 3:49 AM, Zefram wrote:

> >   So we've got around 960 years of the second only

> > being a subdivision of the minute, versus 53 years or so of seconds

> > being more complicated than that.


But really, ever since people started announcing the time publicly,
there have been leaps as they reset those clocks.  For example, the
WWV library
http://www.nist.gov/pml/div688/grp40/hflibrary.cfm
has the many pamphlets about the broadcasts, and as of 1956 it
allows that steps of +-20 ms might be made weekly.  Steps were
completely normal and commonplace.


> And only about 10-15 years where we had computerized time keeping

> that was sufficiently accurate and connected to notice leap seconds.


The big change in the time providing industry was with the advent of
leap seconds.  All of the CCIR recommendations about broadcast time
signals before Rec 460 were descriptive.  Before 460 the regulatory
documents pretty much just summarized the Best Current Practices of
the time service bureaus and broadcasters.

This was evident even with the penultimate CCIR Rec.  before 460, 374
(in 1963) and 374-1 (in 1966).  374 recommended the use of the the
frequency offsets from cesium as coordinated by the BIH, which was a
process already in use by many broadcasts.  374-1 additionally allowed
the use of stepped atomic time (no offset, more frequent steps) which
was another process already in use by broadcasts.

When 374-1 was discussed at the 1967 IAU the folks who knew the CCIR
process were already not communicating clearly with the folks who knew
the time bureau process.  The IAU resolutions from 1967 refer to Rec
374-1 using terminology which did not exist in 374-1, and that is
confusingly sloppy.  Weeks later the CGPM disregarded the request in
the resolution of the IAU, which probably was part of the reason for
the public apology from the BIPM a few years later.

CCIR Rec.  460 was prescriptive, not descriptive, for no existing
broadcasts had tried leap seconds, and the CCIR was constitutionally
not fit for servicing questions from the user community.

--
Steve Allen                 <sla at ucolick.org>                WGS-84 (GPS)
UCO/Lick Observatory--ISB   Natural Sciences II, Room 165    Lat  +36.99855
1156 High Street            Voice: +1 831 459 3046           Lng -122.06015
Santa Cruz, CA 95064        http://www.ucolick.org/~sla/     Hgt +250 m