INTERNATIONAL EARTH ROTATION AND REFERENCE SYSTEMS SERVICE (IERS) SERVICE INTERNATIONAL DE LA ROTATION TERRESTRE ET DES SYSTEMES DE REFERENCE SERVICE DE LA ROTATION TERRESTRE 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 : services.iers@obspm.fr Paris, 8 July 2011 Bulletin C 42 To authorities responsible for the measurement and distribution of time INFORMATION ON UTC - TAI NO positive leap second will be introduced at the end of December 2011. The difference between Coordinated Universal Time UTC and the International Atomic Time TAI is : from 2009 January 1, 0h UTC, until further notice : UTC-TAI = -34 s 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. Daniel GAMBIS Director Earth Orientation Center of IERS Observatoire de Paris, France IMPORTANT: After years of discussions, a proposal to fundamentally redefine UTC will come to a conclusive vote in January 2012 at the ITU-R in Geneva. This proposal would halt the intercalary adjustments known as leap seconds that maintain UTC as a form of Universal Time. The Earth Orientation Center of the IERS organizes a survey online with the objective to find out the strength of opinion for maintaining or changing the present system. Link to the questionnaire: http://hpiers.obspm.fr/eop-pc/index.php?index=questionnaire Your response is appreciated before 30 August 2011 __________________________________________