Warner,
> Yes. I wish it were clearer that TAI time is a regular radio
expression of time.
> Here regular radix means that it every day has 24 hours and every
hour 60 minutes
> and every minute has 60 seconds.
I'm not sure it's fundamental to TAI that one must always, or only, use
24x60x60 radix notation. That's a useful convention in many cases, but
at the h/w counter or s/w binary integer level radix notation is not
required.
The key features of that timescale are its rate, its epoch, its
continuity, and its lack of physical, astronomical, or political
interference. A side effect is that this is a timescale that can be
converted to/from broken-down date/time format in perpetuity using
simple math and without using external tables.
> At the moment there are only two opportunities to consider, though the
> standard allows up to end of every month.
Code should allow for a leap second event at the end of any month. The
June / December thing is one of several guidelines for BIPM; it's not a
rule that anyone writing UTC code should assume or depend on. Nor should
code ever assume leap seconds are positive.
> This ambiguity has lead to bugs when leaps were announced more than 3
months
> in advance. I'd feel better if there were a commitment to these
parameters for some
> number of years. But it's all just convention today.
There's no ambiguity. Those are just bugs. No software should depend on
more than 1 month notice of a leap second and no software should be
fooled if the notice is months or even years in advance.
> Have I forgotten any of the other details of leap seconds that are more
> tribal knowledge than rigorously specified?
If you're writing a FAQ or best practices guide stay in touch. I have a
semi-technical leap second report in the works. UTC is actually very
simple; but it's been complicated by untold levels of bad assumptions,
bad execution, and bad prose.
/tvb
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