The Jargon File (version 4.4.7, 29 Dec 2003):

Great Renaming
 n.

    The flag day in 1987 on which all of the non-local groups on the Usenet
    had their names changed from the net.- format to the current
    multiple-hierarchies scheme. Used esp. in discussing the history of
    newsgroup names. ?The oldest sources group is comp.sources.misc; before the
    Great Renaming, it was net.sources.? There is a Great Renaming FAQ on the
    Web.


The Free On-line Dictionary of Computing (30 December 2018):

Great Renaming

    The flag day in 1986 on which all of the non-local
   groups on the Usenet had their names changed from the net.-
   format to the current multiple-hierarchies scheme.  Used
   especially in discussing the history of newsgroup names.  "The
   oldest sources group is comp.sources.misc; before the Great
   Renaming, it was net.sources."

   FAQ (http://vrx.net/usenet/history/rename.html).

   [Jargon File]

   (2000-07-14)