[LEAPSECS] Leap seconds have a larger context than POSIX

[Michael Deckers]

    On 2020-02-01 23:59, Steve Allen wrote:

> In every instance where a document
> specified a maximum deviation that agreement was later violated.


    The maximum deviation |UTC - UT1| <= 0.9 s as stipulated in
    1974 by CCIR Rec. 460-1 has never been violated until now.

> In one case it was broken specifically because a high official at CCIR
> conceded to a high official from USSR and directed the BIH to violate
> fthe wording of the existing agreement.

    Do you mean the only violation of applicable CCIR rules, the
    introduction of a leap second into UTC at 1973-01-01?

    If so -- this was the choice of using either the date 1973-01-01
    for the insertion of the leap second, or a later date before
    1973-07-01.
       This is evident because at the time, the mean excess length
       of day LOD = d(TAI - UT1)/d(UT1) was observed to be >= 3 ms/d,
       which is more than 0.5 s per 6 months.

    Hence the choice was to either stick with the bound 0.7 s for
    |UT1 - UTC| as required by CCIR Report 517 of 1971, or else stick
    with the primary choices for the possible dates of the insertion
    of leap seconds.

    Apparently, the "high official from USSR" must have preferred
    the latter.

    Michael Deckers.