> Warner Losh scripsit:
> > There's an exception for IERS to
> > step in two weeks in advance if the earth's rotation rate hickups.
> So if I understand this correctly, there could be as many as 14
> consecutive days during which |DUT1| > 0.9s before the emergency leap
> second can be implemented; consequently, the current guarantee is only
> statistical, not absolute.

I think I understand differently.  BIH says on Jan 1 that the
Februrary value of DUT1 is 0.2ms.  If the earth hickups, IERS can step
in by Jan 15th and say, no, the real correct value is 0.3ms.

There's no provision for emergency leapseconds.  They just have to be
at the end of the month, and annoucned 8 weeks in advance.  IERS has
actually exceeded this mandate by announcing them ~24 weeks in advance
in recent history.

The IERS bulletin C is a little different than the ITU TF.460:

>>Leap seconds can be introduced in UTC at the end of the months of  December
>>or June,  depending on the evolution of UT1-TAI. Bulletin C is mailed every
>>six months, either to announce a time step in UTC, or to confirm that there
>>will be no time step at the next possible date.

IERS is issuing Bulletin B as needed.  The latest one can be found at
ftp://hpiers.obspm.fr/iers/bul/buld/bulletind.dat .  Right now DUT1 is
+0.0s until further notice.  From the last few B's, it looks like this
is decreasing at about 300ms per year.  This suggests that the next
leap second will be end of 2008.


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