[time-nuts] FW: Bulletin C number 30

Warner Losh imp at bsdimp.com
Tue Jul 5 12:58:32 EDT 2005

> The main problem is that you can't directly get the UTC - TAI difference,
> right? If you had that, then you could always convert between them.

That's the crux of the matter.  With leap days, I know when to insert
one for the next thousand years or so.  With leap seconds, I have no
clue.  Not only that, I have no way to know the number of leap seconds
that have happened between now and when the device was made unless I
have some communications mechanism to the outside world to tell me.

> There is
> however a peculiarity of which I am sure you are aware of, you would still
> need to know when the leap-seconds occured when doing time-differances over
> possible leap-second insertion points. TAI(t2) - TAI(t1) may not be equalent
> to UTC(t2) - UTC(t1).

Yes.  that's the t1 - t2 problem that I'm talking about.  And the
answer should be identical in both cases (because the leap seconds
actually did happen).  The math is a lot easier if it is all done in
TAI since you don't have to worry about leap seconds complicating the
math.  Or the possible ambiguity that representing a UTC as a single
number can bring with it.


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