Resurrecting the thread with the info on NEOCON I:
It appears to have occurred March 19-21 1982, based on a March 18 1982 article in the Akron Beacon Journal:
The Akron Beacon Journal from Akron, Ohio on March 18, 1982 · Page 41Later years of NEOCON were listed in Dragon magazine's convention calendar, starting with NEOCON III (mentioned in Dragon #83), also in Akron during March, helping to corroborate the accuracy of the newspaper article.
According to the US Copyright Office records, the module was released in January 1983. Search for record number TX0001052082 for details.