[ trim CC: list due to off-topic tangent ] Brian Dickson <brian.peter.dick...@gmail.com> wrote: > > Doesn't UTC actually derive its time from TAI plus/minus leap seconds?
It's more complicated than that :-) Strictly speaking, TAI is a paper clock, which is published as retrospective corrections to national time lab reference clocks. In practice what the general public has access to are time signals that trace back to national versions of UTC, because those are the continuously maintained reference timescales. GNSS time signals are an exception because they mostly lack leap seconds, so their offset from TAI is fixed to within some precision. But GPS time is only roughly TAI-19s. > Why isn't it already available to use as a time zone? Timezones on Unix have to be defined wrt POSIX time (because that's how localtime() works), and POSIX time is a lossy representation of UTC, so you can't get TAI that way without lossage. There were some experiments defining TZ based on a TAI-ish non-standard time_t (the "right" aka wrong timezones) but they aren't usable on a POSIX system. (But note the epoch for the "right" timezones is 10s different from the SMPTE PTP epoch. Sigh.) Tony. -- f.anthony.n.finch <d...@dotat.at> http://dotat.at/ Fisher, German Bight: Southeasterly 5 to 7, increasing gale 8 later. Slight or moderate, becoming rough or very rough later. Showers, rain later. Moderate or good. _______________________________________________ DNSOP mailing list DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop
