12 October 1965: birth of Dan Abnett, author of among others Big Finish audios The Harvest (2004) and Nocturne (2007), Tenth Doctor audio stories The Forever Trap (2008) and The Last Voyage (2010), Torchwood audio Everyone Says Hello (2008), most of the Tenth Doctor book The Story of Martha (2008), and Torchwood novel Border Princes (2007) plus various other comics and short stories.
ii) broadcast anniversaries
12 October 1968: broadcast of episode 5 of The Mind Robber. A grand battle of fictional characters allied to either the Doctor or the Master ends with the destruction of the Land of Fiction and the restoration of the Tardis.
12 October 1987: broadcast of episode 2 of Paradise Towers. The Doctor escapes the caretakers, seeks the Great Architect and is captured by the Red Kangs; meanwhile Mel is captured by Tibby and Tabby.
12 October 2010: broadcast of episode 2 of The Nightmare Man (Sarah Jane Adventures). And it's farewell to Luke, after much exploration of nightmares and dark places; if there had been more episodes of SJA, there was going to be a story where he turned out to be gay.
iii) dates specified in canon
12 October 1979: Beep the Meep pursues the Eighth Doctor to the BBC Television Centre in an alternate universe where they encounter an actor called Tom Baker who is starring in this show... (in "TV Action!" by Alan Barnes, published in DWM in 1999)
12 October 1998: birth of Thomas Hector Schofield, later to become known as the Seventh Doctor audio companion Hex; he shares a birthday with his creator Dan Abnett (see above).
12 October 2021: Hex's 23rd birthday celebrations are interrupted by Cybermen in The Harvest (2004).
12 October 2025: Hex returns home in Project: Destiny (2010).