[LEAPSECS] BBC radio Crowd Science

[Zefram]

Warner Losh wrote:
>Saying that the two numbers are the same is improper. Or rather, it
>depends on which time scale you are looking at them in if they are
>improper.

The numbers are not on any time scale.  The numbers are derived from
the time values, but are a different thing.

>However, if you look at the two times in UTC land and compute a delta
>in UTA land, then you find the interval between N:23:59:60 and
>N+1:00:00:00 you wind up with 1 second. That leads to the conclusion
>that the difference starts at the beginning of the leap second.

It does not lead to that conclusion in the general case.  (It does for
the specific case of TAI-UTC changing from 0 s to 1 s.)  This is one of
the options for handling TAI-UTC that I examined a few messages ago,
and it leads to the conclusion that if TAI-UTC is initially positive
then it increases some seconds *before* the leap second.  I'd examined it
because it appeared to me that, by consistently using the irregular radix
for subtraction, it was applying the principle that you were claiming to
apply, though it leads to a different conclusion from the one you reached.
(You responded that this was not your system.)

I'd still like to see from you a worked example of TAI-UTC for a time a
few seconds before a positive leap second, where TAI has already ticked
over into the following day, to compare against an equivalent example
for a time inside the same positive leap second.  You've done a worked
example inside a leap second, but not one in the preceding seconds.
I want to see how you get a different result for 00:00:35-23:59:59 from
that which you get for 00:00:36-23:59:60.

>can't normalize N:23:59:60 to N+1:00:00:00 because in UTC they are two
>different second labels.

They certainly are different second labels, and in UTC they even
label different seconds.  That's not in dispute.  I did not normalise
one of them to the other.  The equivalence between them is only that
certain relevant functions of UTC time labels, specifically MJD and its
equivalents, yield the same value for both of these.  It is via those
functions that TAI-UTC is tacitly defined.

>                                                               Which
>one of those is 0h?

The instant of 0h is 00:00:00.

-zefram