21 December (releases)


 * 1963 - "The Dead Planet", the first episode of The Daleks, was first broadcast on BBC tv. Dalekmania began.
 * 1964 - Part seven of the comic story The Klepton Parasites was first published in the 680th issue of TV Comic.
 * 1965 - The stage play The Curse of the Daleks premièred at Wyndham's Theatre.
 * 1968 - Episode eight of The Invasion was first broadcast on BBC1.
 * 1968 - Part four of the TV Comic story Jungle of Doom was first published.
 * 1974 - Part three of the TV Comic story The Wanderers was first published.
 * 1988 - Part two of The Greatest Show In The Galaxy was first broadcast on BBC1.
 * 1989 - The novelisation of The Greatest Show in the Galaxy was released by Target Books.
 * 1995 - DWM 234 was first released by Marvel Comics.
 * 1996 - Part ten of the Radio Times comic story Ascendance was first published.
 * 2011 - Part two of Attack of the Snowmen was first published online.
 * 2012 - Songtaran Carols was first released online.
 * 2014 - Part three of Behind You was first published online.
 * 2014 - Toby Hadoke's Who's Round 98 was released online.
 * 2015 - Part one of Haunted was first published online.
 * 2017 - Toby Hadoke's Who's Round 231 was released online.
 * 2018 - The Devil's Footprints was first released by Big Finish Productions.
 * 2020 - Incoming Transmission was first released online.