1966

January

 * 1 - The TARDIS departed Trafalgar Square, where it had arrived during the New Year's Eve celebrations. (TV: The Daleks' Master Plan)

July

 * 5 - Ben Jackson began a five-month shore posting. (TV: The War Machines)
 * 12 through 20 - From its base in the Post Office Tower in London, WOTAN directed mind-controlled human and robot War Machines. (TV: The War Machines)
 * 20 - The First Doctor and Dodo Chaplet arrived in London and battled the War Machines. The Doctor left with new companions Polly Wright and Ben Jackson. (TV: The War Machines) After defeating WOTAN, the Doctor checked to see if the Hand of Omega had been buried in Shoreditch Cemetery as per his instructions in November 1963, only to discover that it has been removed. He determined that his future self would arrive at an earlier point in order to deal with it. (PROSE: The Rage and Bone Man's Story)
 * The Second Doctor, Ben, Polly and Jamie McCrimmon became involved with the schemes of the Chameleons at Gatwick Airport. Ben and Polly decided to stay behind in their own time. (TV: The Faceless Ones) Meanwhile, the Daleks stole the TARDIS. (TV: The Evil of the Daleks)
 * The Ninth Doctor and Rose Tyler visited London. (COMIC: The Love Invasion)

Unknown dates

 * The Doctor's TARDIS and the Dalek time machine materialised on an observation deck of the Empire State Building. (TV: The Chase)
 * During the summer, on Thursdays, the first eleven incarnations of the Doctor visited artist Andy Warhol individually. Warhol painted them on one painting. (WC: The War of Art)
 * Peri Brown, a companion of the Doctor during his fifth and sixth incarnations, was born to Paul and Janine Brown. (TV: Planet of Fire, AUDIO: The Reaping)
 * Tony Barker, Amy Barker and Butch stowed away on the Doctor's TARDIS. (PROSE: The Monsters from Earth)
 * Katherine Chambers was born. (AUDIO: The Reaping)
 * The Fifth Doctor dropped off his companions Peri Brown and Erimem in Monte Carlo and instructed them to prevent the Veiled Leopard from being stolen while the Seventh Doctor's companions Ace and Hex were simultaneously trying to steal it. However, the two sets of companions did not interact and remained ignorant of what they had in common. (AUDIO: The Veiled Leopard)

January

 * 01 - "Volcano" (TV: The Daleks' Master Plan Episode 8) was first broadcast.
 * 08 - "Golden Death" (TV: The Daleks' Master Plan Episode 9) was first broadcast.
 * 15 - "Escape Switch" (TV: The Daleks' Master Plan Episode 10) was first broadcast.
 * 12 - The final part of COMIC: The Didus Expedition was released.
 * 22 - "The Abandoned Planet" (TV: The Daleks' Master Plan Episode 11) was first broadcast.
 * The first part of COMIC: The Didus Expedition was released.
 * 29 - "Destruction of Time" (TV: The Daleks' Master Plan Episode 12) was first broadcast. Jean Marsh left the series as her character, Sara Kingdom, became the second companion to die in the line of duty.
 * 30 - Daphne Ashbrook (Grace Holloway in the TV movie) was born in Long Beach, California.

February

 * 05 - "War of God" (TV: The Massacre of St Bartholomew's Eve Episode 1) was first broadcast.
 * 12 - "The Sea Beggar" (TV: The Massacre of St Bartholomew's Eve Episode 2) was first broadcast.
 * 19 - "Priest of Death" (TV: The Massacre of St Bartholomew's Eve Episode 3) was first broadcast.
 * The first part of COMIC: Space Station Z-7 was released.
 * 26 - "Bell of Doom" (TV: The Massacre of St Bartholomew's Eve Episode 4) was first broadcast. Jackie Lane made her debut as companion Dodo Chaplet.

Early 1966

 * Exact date unknown - William Hartnell sent shockwaves through the Doctor Who production team by announcing his intention to leave the series. Over the following months, producers and writers developed the concept of regeneration to explain the change of lead actor and cast Patrick Troughton as the new Doctor; Hartnell eventually agreed to appear in the first two serials of the new season.

March

 * Dalek Action Paint 'n Puzzle was published by Souvenir Press.
 * Dr. Who Travels in Space Sticker Fun Book was published.
 * Dr. Who Travels in Time Sticker Fun Book was published.
 * 05 - "The Steel Sky" (TV: The Ark Episode 1) was first broadcast.
 * 12 - "The Plague" (TV: The Ark Episode 2) was first broadcast.
 * The final part of COMIC: The Didus Expedition was released.
 * 19 - "The Return" (TV: The Ark Episode 3) was first broadcast.
 * The first part of COMIC: Plague of the Black Scorpi was released.
 * 26 - "The Bomb" (TV: The Ark Episode 4) was first broadcast.

April

 * Century 21 Records released a Doctor Who edition of its 21 Minutes of Adventure LP record series, featuring the audio soundtrack of "The Planet of Decision", a chapter of TV: The Chase. It was the first audio story to be made available for sale.
 * 02 - "The Celestial Toyroom" (TV: The Celestial Toymaker Episode 1) was first broadcast.
 * 09 - "The Hall of Dolls" (TV: The Celestial Toymaker Episode 2) was first broadcast.
 * The final part of COMIC: Plague of the Black Scorpi was released.
 * 16 - "The Dancing Floor" (TV: The Celestial Toymaker Episode 3) was first broadcast.
 * 23 - "The Final Test" (TV: The Celestial Toymaker Episode 4) was first broadcast.
 * 30 - "A Holiday for the Doctor" (TV: The Gunfighters Episode 1) was first broadcast.

May

 * The Doctor Who production office circulated a memo to writers outlining the proposed character of the Second Doctor, as well as suggestions on handling the first regeneration, which was initially compared to an LSD trip gone bad.
 * 07 - "Don't Shoot the Pianist" (TV: The Gunfighters Episode 2) was first broadcast.
 * 14 - "Johnny Ringo" (TV: The Gunfighters Episode 3) was first broadcast.
 * 20 - Mervyn Pinfield, a director and associate producer for Doctor Who, died.
 * 21 - "The OK Corral" (TV: The Gunfighters Episode 4) was first broadcast. This marked the final time individual episode titles would be used in the original series (the practice would resume in 2005).
 * 28 - TV: The Savages Episode 1 was first broadcast.

June

 * 04 - TV: The Savages Episode 2 was first broadcast.
 * 11 - TV: The Savages Episode 3 was first broadcast.
 * 18 - TV: The Savages Episode 4 was first broadcast. Peter Purves left the series with this episode, although he would continue his association with Doctor Who for years to come when he subsequently became co-host of Blue Peter, often presenting promotional features about the series.
 * 19 - Sam West (Cyrian in NOTDWU: Dimensions in Time) was born.
 * 25 - TV: The War Machines Episode 1 was first broadcast. Michael Craze and Anneke Wills made their debuts as Ben Jackson and Polly, respectively. This episode was notorious for having a character -- the computer WOTAN -- break the longstanding taboo of referring to the Doctor as "Doctor Who".

July

 * 02 - TV: The War Machines episode 2 was first broadcast. This was the final appearance of Jackie Lane as Dodo Chaplet.
 * 09 - TV: The War Machines Episode 3 was first broadcast.
 * 16 - TV: The War Machines Episode 4 was first broadcast, concluding the third season.
 * The film Dr. Who and the Daleks was released to theatres in the United States. For most audiences in America, this was their first exposure to the Doctor Who concept, as the TV series had not as of this date been broadcast in the US (although some communities bordering Canada were able to view the series on the CBC network).
 * 30 - Jason Watkins, a voice actor for Big Finish Productions, was born.

August

 * 05 - The second feature film, Daleks' Invasion Earth 2150 A.D., based upon TV: The Dalek Invasion of Earth, was released in the UK.

September

 * The second Doctor Who Annual was published.
 * 08 - The Dalek Outer Space Book was first published.
 * Star Trek debuted in America. This influential series would become Doctor Who's chief rival in terms of franchise longevity, although the original series would only run until the spring of 1969.
 * 10 - TV: The Smugglers Episode 1 was first broadcast, marking the beginning of Season 4.
 * 17 - TV: The Smugglers Episode 2 was first broadcast.
 * 24 - TV: The Smugglers Episode 3 was first broadcast.

October

 * 01 - TV: The Smugglers Episode 4 was first broadcast.
 * 08 - TV: The Tenth Planet Episode 1 was first broadcast, marking the first appearance of the Cybermen.
 * Episode 4 of TV: The Tenth Planet was taped, with the first scenes filmed being the regeneration from William Hartnell (making his final regular appearance as the First Doctor) to Patrick Troughton (making his first appearance as the Second Doctor).


 * 15 - TV: The Tenth Planet Episode 2 was first broadcast.
 * 17 - Mark Gatiss was born.
 * 22 - TV: The Tenth Planet Episode 3 was first broadcast.
 * Episode 1 of TV: The Power of the Daleks was taped; this was the first full episode featuring Patrick Troughton.


 * 29 - TV: The Tenth Planet Episode 4 was first broadcast, ending in the first regeneration, from William Hartnell to Patrick Troughton, shocking children across Britain.

November

 * 05 - TV: The Power of the Daleks Episode 1 was first broadcast. This was Patrick Troughton's first full episode as the Second Doctor, although William Hartnell briefly appears as a mirror reflection.
 * 12 - TV: The Power of the Daleks Episode 2 was first broadcast.
 * 19 - TV: The Power of the Daleks Episode 3 was first broadcast.
 * 22 - Nicholas Rowe, who voiced Rivesh Mantilax in TV: Dreamland, was born.
 * 26 - TV: The Power of the Daleks Episode 4 was first broadcast.

December

 * 03 - TV: The Power of the Daleks Episode 5 was first broadcast.
 * 10 - TV: The Power of the Daleks Episode 6 was first broadcast.
 * 12 - The BBC Audience Research Dept. filed an Audience Research Report on TV: The Power of the Daleks Episode 3, reporting that satisfaction in the episode ranked at 44% with response to new Doctor Patrick Troughton being particularly mixed.
 * 15 - Patrick Troughton was interviewed in Radio Times.
 * 17 - TV: The Highlanders Episode 1 was first broadcast. Frazer Hines debuted as new companion Jamie McCrimmon.
 * 24 - TV: The Highlanders Episode 2 was first broadcast.
 * 31 - TV: The Highlanders Episode 3 was first broadcast.

Unknown dates

 * Doctor Who and the Invasion from Space was published by World Distributors. A hardcover novella, this was the first publication of an original long-form text story to feature the First Doctor. (It was presumably published prior to October as it featured the First Doctor.)
 * US comic book publisher Dell Comics issued a single-issue adaptation of the Dr. Who and the Daleks film. This was the first (and, until the early 1980s, only) appearance of a Doctor Who-related comic book in the US.