Dating protocol

Due to the various temporal discrepancies in the 1970s and 1980s, a dating protocol was created by the United Nations for their files. It was established in January 1990 at a secret meeting in Geneva between Alistair Gordon Lethbridge-Stewart, Charles Crichton, and Amara Essy. (PROSE: The Enfolded Time)

Events covered by the protocol
A number of events were filed as occurring at two different equally valid dates during the years covered by the protocol:
 * The Great Intelligence's invasion of London (TV: The Web of Fear) occurred in February 1969 and March 1975. (PROSE: The Enfolded Time)
 * The dinosaur invasion of London (TV: Invasion of the Dinosaurs) occurred in 1974 and 1979. (PROSE: The Enfolded Time)
 * The attack on an environmental peace conference by Zygons occurred in both the 1970s and the 1980s. (TV: The Day of the Doctor, Terror of the Zygons)
 * Brigadier Lethbridge-Stewart retired from UNIT in both 1976 (TV: Mawdryn Undead) and 1981. (PROSE: The Enfolded Time)

Behind the scenes
The United Nations dating protocol is a reference to the UNIT dating controversy, a source of interest and argument among writers and fans.