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Pure Appl. Chem., 2011, Vol. 83, No. 5, pp. 1159-1162

Published online 2011-04-08

IUPAC-IUGS common definition and convention on the use of the year as a derived unit of time (IUPAC Recommendations 2011)

Norman E. Holden1,2, Mauro L. Bonardi1,3, Paul De Bièvre4,1, Paul R. Renne5,6,7 and Igor M. Villa8,7,9*

1 International Union of Pure and Applied Chemistry
2 National Nuclear Data Center, Brookhaven National Laboratory, Upton, NY 11973, USA
3 LASA, Università degli Studi di Milano and INFN, I-20090 Segrate, Italy
4 Consultant on Metrology in Chemistry, Duineneind 9, B-2460 Kasterlee, Belgium
5 Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94720, USA
6 Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, USA
7 International Union of Geological Sciences
8 Institut für Geologie, Universität Bern, CH-3012 Bern, Switzerland
9 Università di Milano Bicocca, I-20126 Milano, Italy


  • 1. IUPAC. Quantities, Units and Symbols in Physical Chemistry, 3rd ed. (the “Green Book”). Prepared for publication by E. R. Cohen, T. Cvitaš, J. G. Frey, B. Holmström, K. Kuchitsu, R. Marquardt, I. Mills, F. Pavese, M. Quack, J. Stohner, H. L. Strauss, M. Takami, A. J. Thor, p. 137, RSC Publishing, Cambridge, UK (2007).
  • 2. IUPAP. Symbols, Units and Nomenclature and Fundamental Constants in Physics, <>.
  • 3. Recommendations concerning Units. Reprinted from the “IAU Style Manual” by G. A. Wilkinson, Comm. 5, in IAU Transactions XXB (1987). <>.
  • 4. A. Thompson, B. N. Taylor. Special Publication 811: Guide for the Use of the International System of Units (SI), National Institute of Standards and Technology (NIST), Gaithersburg, MD, USA (2008).
  • 5. BIPM. Le Système international d’unités – The International System of Units SI, 8th ed., Bureau International des Poids et Mesures, Geneva (2006). <>.
  • 6. The 11th General Conference on Weights and Measures (GGPM), Resolution 9; CR 86 (1960).