The NIST Reference on Constants, Units and Uncertainty

Constants,
Units &
Uncertainty
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Version history

    Changes to the databases
    For details about how the values of the fundamental constants and the bibliographic citations have changed, see version histories of the fundamental constants database and the bibliographic database.

    Changes to editorial content
    20 May 2019   The 2018 values provided, 2014 values transferred to archived tables.
    25 June 2015   The 2014 values provided, 2010 values transferred to archived tables.
    2 June 2011   The 2010 values provided, 2006 values transferred to archived tables.
    9 March 2007   The 2006 values provided, 2002 values transferred to archived tables.
    9 December 2003   The 2002 values provided, 1998 values transferred to archived tables.
    23 July 1999   The 1998 values provided, 1986 values transferred to archive page.
    17 June 1999   Binary prefixes added to SI Units section.
    19 October 1998   Minor editorial additions. Feedback and links pages updated. Links to online unit conversions introduced.
    17 February 1998   Site established.

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