> > > On 27 Nov 2018, at 1:54 am, Tony Finch <d...@dotat.at> wrote:
> > > > Richard Gibson <richard.j.gib...@oracle.com> wrote: > >> > >> I am currently going through a similar exercise in another context, and the > >> best current text there explicitly characterizes the non-obvious day-based > >> accounting of POSIX time. > > > > In general I think it's best to just refer to POSIX on this matter, and > > not try to restate the definition. POSIX is very clear and explicit about > > the day-based accounting of seconds. > > > > http://pubs.opengroup.org/onlinepubs/9699919799.2016edition/basedefs/V1_chap04.html#tag_04_16 > > > >> However, there may be C-DNS purposes that cannot tolerate such > >> discontinuities, and they would presumably want to use a continuous monotonic > >> timescale with a fixed offset from TAI (as is the case for e.g. GPS time). > > > > That's practically unobtanium on most systems :-) Even if you have PTP > > there isn't a fixed PTP epoch, though the SMPTE profile defines it to be > > equivalent to POSIX time plus the TAI-UTC value from the IERS / NIST > > leapsecond tables. > IMHO, this (the SMTPE profile) makes the most sense. The most important aspect is that it is continuous, and the second most important is that it relates predictably to UTC. Honestly, the whole "leap second" thing... don't get me started. But, I think it would be fair to have "this thing" (what the formula describes) be its own "time zone", i.e. that it be given a proper representation everywhere that anything that uses some notion of "local time", can refer to time using that as a TZ. I'd suggest that C-DNS start using it, and parallel to that, propose the reference timeframe be adopted by whatever WG or standards body manages timezones and/or UTC. Besides, isn't it kind of backwards? Doesn't UTC actually derive its time from TAI plus/minus leap seconds? Why isn't it already available to use as a time zone? (Consults wikipedia on unix time, sees there is an IANA database. Curses POSIX.) Brian > Tony. > > -- > > f.anthony.n.finch <d...@dotat.at> http://dotat.at/ > disperse power, foster diversity, and nurture creativity
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