INTERNATIONAL EARTH ROTATION SERVICE (IERS)
SERVICE INTERNATIONAL DE LA ROTATION TERRESTRE


BUREAU CENTRAL DE L'IERS
OBSERVATOIRE DE PARIS
61, Av. de l'Observatoire 75014 PARIS (France)
Tel.      : 33 (0) 1 40 51 22 26
FAX       : 33 (0) 1 40 51 22 91
Internet  : iers@obspm.fr




Paris, 17 July 1998




Bulletin C 16


To authorities responsible for
the measurement and distribution
of time




UTC TIME STEP
on the 1st of January 1999




A positive leap second will be introduced at the end of December 1998.
The sequence of dates of the UTC second markers will be:


1998 December 31,     23h 59m 59s
1998 December 31,     23h 59m 60s
1999 January   1,      0h  0m  0s


The difference between UTC and the International Atomic Time TAI is:


from 1997 July 1,    0h UTC, to 1999 January 1, 0h UTC  : UTC-TAI = - 31s
from 1999 January 1, 0h UTC, until further notice       : UTC-TAI = - 32s


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 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.






Daniel GAMBIS
Director
Central Bureau of IERS