NavList:

Actually, getting back to more "practical" matters (so far as what this group considers "practical"), this has the potential to be a mess for CelNav.

As noted on page 254 of the Nautical Almanac, "The time argument on the daily pages... is UT1."  The nautical almanac offices will need to decide if they want someone to blow the dust off of the automated routines that produce these almanacs and decide whether to keep the tables at UT1 or change them to New UTC specifically.

They may be compelled to change to New UTC if that ends up being what radio time broadcasts end up moving to (otherwise there'd be an added step of "subtract X seconds before entering the Increments & Corrections Tables").  However, the change itself has the potential to break radio time broadcasts themselves.  The signals typically have information on UT1-UTC encoded into the signals (e.g. the "double ticks" I can hear in WWV and CHU), but the encoding systems were never intended for that difference to exceed +/- 0.9 s.

Humans can adjust to the change in time signal formats, but the hard-wired "atomic clocks" that rely on longwave radio signals can't.  Any change in the signal format might cause these timepieces to malfunction in ways that users might not even be aware of.

In the US, I think power plants on the electrical grid *still* aren't allowed to alter their alternating current timings in a way that might break synchronous clocks, which rely on 1 day being 86,400 s * 60 Hz cycles long, and those clocks went away around the time one could literally get a quartz watch from buying breakfast cereal.

("How I Learned to Stop Worrying and Love Stark's Tables")