[LEAPSECS] USWP7A docs for 2013 September meetings

[Zefram]

Warner Losh wrote:

>That is unless the API explicitly says "always hide leap seconds from

>users in this way"...


That's basically what it says.  The API is based around a single base
time scale, which in the present era is UTC-SLS.  The only way leap
seconds would matter for a computation with JSR-310 would be if you
converted between its time scale and some other time scale such as TAI.
No such conversion is available through the API, so that doesn't arise.
Computations within the time scale, which are the main business of the
API, are unaffected by leap seconds, because they use the seconds of
UTC-SLS without caring that some of them are of different lengths when
looked at in a different way.

The only place where leap seconds directly affect the operation of
the API is where you ask a Clock object what the current time is.
It must reply in UTC-SLS, thus hiding leap seconds in the standard way.
But implementations aren't obliged to provide an accurate clock.  If they
don't advertise that a clock is sub-second accurate, then a POSIX-like
discontinuity around leap seconds is acceptable, just as it's acceptable
for the clock to give readings that are minutes off.

-zefram