[LEAPSECS] next leap second

[Zefram]

John Sauter wrote:
>While it is impossible to know for certain when the next leap second
>will occur, I predict it will be December 31, 2022.

I find that a surprising prediction.  What is your basis for it?

The extrapolating expression from the current Bulletin A
<https://datacenter.iers.org/eop/-/somos/5Rgv/getTX/6/bulletina-xxx-001.txt>,
which projects a linear evolution of UT2-TAI, suggests that UT1-TAI
will approach -37.5 in early 2019 (actually passing it on 2019-02-03),
and then pass that value twice more early in the second half of 2019.
So I'd expect the next leap second to happen on 2018-12-31 or 2019-06-30.
If there is no leap, this projection suggests that the UT1-UTC bound would
be exceeded on 2020-01-19.  Extending all the way out to your proposed
leap date, which is a dubious exercise given the crudity of the model,
yields UT1-TAI ~= -39.228 at 2023-01-01, implying that we'd need to have
two leaps between now and then, with 2022-12-31 being an early candidate
for the *third* leap from now.

-zefram