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Provisional Recommendations

Joint IUPAC-IUGS Task Group On Isotope Data In Geosciences

Convention on the Use of Units for Time in Earth and Planetary Sciences

The units of time (both absolute time and duration) most practical to use in Earth and Planetary Sciences are multiples of the year, or annus (a). Its proposed definition in terms of the fundamental SI unit for time, the second (s), for the epoch 2000.0 is 1 a = 3.1556925445 × 107 s. Adoption of this definition, and abandonment of the use of distinct units for time differences, will bring the Earth and Planetary Sciences into compliance with the SI standard regarding units of time.

> Download full text of the Provisional Recommendations (pdf file - 155KB)

Comments by 30 June 2009
To Dr. Igor Villa
Institut für Geologie
Universität Bern
CH-3012 Bern, Switzerland
E-mail: igor@geo.unibe.ch

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