I may have more comments soon, but here is one about the initial
definitions as this proposed SRFI does want to do everything right if
possible (which is a good thing IMO):

Reading the definition of the TAI calendar, it can sound as if there
were an absolute time (otherwise, the phrase "every 86,400 SI seconds"
would not make sense). However, atomic clocks are precise enough to
detect the derivations of Newtonian mechanics from special and general
relativity. As there is no god-given absolute clock one has to take an
arbitrary clock as a reference. A suitable reference is precisely the
TAI clock, measuring seconds since the event that is called "1 January
1958" in the TAI calendar. Note that the phrase "at midnight on 1
January 1958" does not make sense before the definition of any
calendar (or, at least, has the danger of being a self-referential
definition).

With the TAI clock set as a reference, the TAI and the UTC calendar
can then be derived through simple arithmetic.

Am Fr., 3. Jan. 2025 um 13:43 Uhr schrieb Daphne Preston-Kendal
<xxxxxx@nonceword.org>:
>
> I have posted a new version of the pre-SRFI. Apart from the changes mentioned in my mail to Antero, I have also added local ‘clock-times’ as requested by Arthur, and explicitly noted the ISO 8601 correspondences for each data type provided. Also, there’s now a helpful table of contents at the top so the structure can be seen more easily.
>
> <https://gitlab.com/dpk/presrfis/-/blob/master/date-time.md>
>
> Apart from the specifications of procedures which currently have a header line only, whose meaning should generally be obvious from the name, I think this is a reasonably good starting point to begin to move towards SRFI submission. At the very least, the data model feels good, which is the main thing I was concerned about getting right in advance before moving towards submission, and thus implementation.
>
> If there are no major objections, I will give Arvydas the green light to start working on implementing the rest of the spec, and then we’ll submit as soon as he feels ready.
>
>
> Daphne
>