On 2011-02-01 11:35, Poul-Henning Kamp wrote:
Thanks to leap-seconds we do not know how long (certain) minutes are, until Daniel tells us.
Daniel Gambis does not define certain time units, he just communicates the difference TAI - UTC as soon as it becomes known for another six months.
"UTC is unpredictable" is the core of the problem, and a problem that must be solved, either by extending the predictability horizon from six months to at least 10 years, or by making UTC predictable.
What currently is unpredictable far into the future is the difference TAI - UTC. Now the difference TAI - TT is also unpredictable -- but is that a reason to say that either TAI or TT is unpredictable, or to redefine one of them? As far as the civil uses of time scales are concerned, it is actually UTC rather than TAI that is currently more "predictable": I can predict with great certainty that I shall attend a group meeting when UTC will be 2012-01-30 + 09 h, but TAI at that instant is currently only known with an uncertainty of 1 s. How could the unpredictable difference TAI - UTC be a problem if everybody (including every computer) just kept UTC? Michael Deckers. _______________________________________________ LEAPSECS mailing list [email protected] http://six.pairlist.net/mailman/listinfo/leapsecs
