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

@article{Holden2011IUPACIUGSCD,
  title={IUPAC-IUGS common definition and convention on the use of the year as a derived unit of time (IUPAC Recommendations 2011)},
  author={Norman E. Holden and M. Bonardi and Paul De Bi{\'e}vre and Paul R. Renne and Igor Maria Villa},
  journal={Pure and Applied Chemistry},
  year={2011},
  volume={83},
  pages={1159 - 1162}
}
The units of time (both absolute time and duration) most practical to use when dealing with very long times, for example, in nuclear chemistry and earth and planetary sciences, are multiples of the year, or annus (a). Its proposed definition in terms of the SI base 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… 
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