Memorandum: Date change of mail meeting
RFC 456, “Memorandum: Date change of mail meeting”, is an Unknown document published in February 1973 by M.D. Kudlick. The canonical text is published by the RFC Editor.
What “Unknown” means
The standards-track status of this early RFC was never formally classified.
The canonical text of RFC 456 is hosted at rfc-editor.org. Available in TXT,HTML.