FCC KDB 822428, released on 11 August 2017, says (in part):
The C63® committee has a newsletter that shows the latest news and information about C63® and its activities. Read the lastest issues at http://www.c63.org/documents/c63/list_of_newsletters.htm for information about the most recent changes to C63® standards.
ANSI C63.5-2017 was recently released and is to be used for calibrating measurement antennas.
For FCC compliance measurements, a transition period will be allowed such that measurement antennas used for radiated emission measurements may be calibrated in accordance with either ANSI C63.5-2006 or ANSI C63.5-2017 during the transition period.
After August 1, 2018, measurement antennas are required to be calibrated in accordance with ANSI C63.5-2017.