[LEAPSECS] Inside GNSS published an update of my CGSIC talk

[Michael Deckers]

    On 2023-03-20 07:54, Jürgen Appel via LEAPSECS wrote:


> In your Conclusion, you say "the CGPM resolution also stipulates that no
> change to current practices can occur before 2035."
>
> This is not how I read read the CGPM document on the BIPM website:
> "The General Conference on Weights and Measures (CGPM), at its 27th meeting
> [...] decides that the maximum value for the difference (UT1-UTC) will be
> increased in, or before, 2035,"
>
> So in case the negative leap seconds become a real threat, according to my
> interpretation is is an option to increase the tolerance value earlier than
> 2035 to avoid trying out negative leap seconds a last and first time.
>
> Can someone confirm my view?



     You read correctly, the French (official) version has

        ..."décide que la valeur maximale pour la différence
            (UT1 - UTC) sera augmentée au plus tard en 2035,"....

     which means "in 2035 at the latest".

     Note also that the definition of UTC as approved by the
     CGPM never mentions _any_ explict bound for |UT1 - UTC|; it
     only says that (TAI - UTC) is an integral multiple of 1 s
     as determined by the IERS. It is the IERS who state that

        "Coordinated Universal Time (UTC) a measure of time
         that conforms, within approximately 1 s, to the mean
         diurnal motion of the Sun and serves as the basis of
         all civil timekeeping."

     quoting the IAU "Nomenclature for Fundamental Astronomy (NFA)"
     found at http://syrte.obspm.fr/iauWGnfa/NFA Glossary.html.

     This seems to be lenient enough to allow for not scheduling
     a negative leap second even in the case that the difference
     (UT1 - UTC) should go a bit below -1 s before 2035.

     Michael Deckers.