Bayley, Alistair Alistair_Bayley at ldn.invesco.com
Wed Jan 26 10:28:14 EST 2005

> From: Peter Simons [mailto:simons at cryp.to] 
> Well, there _is_ an absolute notion of time, that is what TAI is.
> The reason why that seems to be of little use for the general
> public is that this absolute time scale just doesn't correspond
> to calendar time. There simply is no accurate mapping between TAI
> and the information 2043-04-01T00:00:00.

I assume that the only reason we can't establish a mapping between
2043-04-01T00:00:00 and TAI is because of the leap seconds problem. I assume
we can map accurately between TAI and (say) 2001-01-01T00:00:00 (Gregorian).
And I assume that we just accept that the TAI <-> UTC/Gregorian/whatever
mapping cannot be accurate for times in the future.

My point was that when you say "here is a time, specified as x", where x is
one of TAI / UTC / Julian+TZ / Gregorian+TZ / etc, any of the x's is as good
as any other (as long as the time is not in the future), and the internal
representation of time could be any one of, or none of x. I think people are
proposing TAI as an internal representation, but it's not necessary, and I'm
wondering if it's even desirable.

What are the limits on a 64bit TAI implementation? 64 bits gives you (signed
  +/- 9223372036854775807:

Assuming milliseconds (is this reasonable?):
 922337203685477.5807 secs
 ~= 106751991167 days
 ~= 292471208 years

OK, that seems plenty...

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