23 January

On 23 January 1963, Kim Philby disappeared. (PROSE: Endgame)

In the Daft Dimension, an issue of Televisual Comic was dated to 23 January 1965, a Monday. (COMIC: The Secret History of Life Before Doctor Who Magazine!)

Behind the scenes
Despite what is shown in The Secret History of Life Before Doctor Who Magazine!, 23 January actually fell on a Saturday in 1965.