1966

January

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

July

 * 5 - Ben Jackson began a five month shore posting. (DW: 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. (DW: The War Machines)
 * 20 - The Second Doctor, Polly, Ben Jackson and Jamie McCrimmon got involved with the schemes of the Chameleons at Gatwick Airport. Ben and Polly decided to stay behind in their own time. (DW: The Faceless Ones) Meanwhile, the Daleks stole the Doctor's TARDIS. (DW: The Evil of the Daleks)

Unknown date

 * The Doctor's TARDIS and the Dalek time machine materialised on an observation deck of the Empire State Building. (DW: The Chase)
 * The Ninth Doctor and Rose Tyler visited London. (DWM: The Love Invasion)
 * Ace and Hex met Peri Brown and Erimem. (BFA: The Veiled Leopard)
 * 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)
 * Birth of Peri Brown, companion of the Doctor in his fifth and sixth incarnations. (DW: Planet of Fire)

January

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

February

 * 05 - "War of God" (DW: The Massacre of St Bartholomew's Eve Episode 1) was first broadcast.
 * 12 - "The Sea Beggar" (DW: The Massacre of St Bartholomew's Eve Episode 2) was first broadcast.
 * 19 - "Priest of Death" (DW: The Massacre of St Bartholomew's Eve Episode 3) was first broadcast.
 * 26 - "Bell of Doom" (DW: 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 sends 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

 * Publication of Dalek Action Paint 'n Puzzle by Souvenir Press.
 * Publication of Dr. Who Travels in Space Sticker Fun Book.
 * Publication of Dr. Who Travels in Time Sticker Fun Book.
 * 05 - "The Steel Sky" (DW: The Ark Episode 1) was first broadcast.
 * 12 - "The Plague" (DW: The Ark Episode 2) was first broadcast.
 * 19 - "The Return" (DW: The Ark Episode 3) was first broadcast.
 * 26 - "The Bomb" (DW: 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 DW: The Chase. It was the first audio story to be made available for sale.
 * 02 - "The Celestial Toyroom" (DW: The Celestial Toymaker Episode 1) was first broadcast.
 * 09 - "The Hall of Dolls" (DW: The Celestial Toymaker Episode 2) was first broadcast.
 * 16 - "The Dancing Floor" (DW: The Celestial Toymaker Episode 3) was first broadcast.
 * 23 - "The Final Test" (DW: The Celestial Toymaker Episode 4) was first broadcast.
 * 30 - "A Holiday for the Doctor" (DW: 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" (DW: The Gunfighters Episode 2) was first broadcast.
 * 14 - "Johnny Ringo" (DW: The Gunfighters Episode 3) was first broadcast.
 * 21 - "The OK Corral" (DW: 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 - DW: The Savages Episode 1 was first broadcast.

June

 * 04 - DW: The Savages Episode 2 was first broadcast.
 * 11 - DW: The Savages Episode 3 was first broadcast.
 * 18 - DW: 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.
 * 25 - DW: 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 - DW: The War Machines episode 2 was first broadcast. Final appearance of Jackie Lane as Dodo Chaplet.
 * 09 - DW: The War Machines Episode 3 was first broadcast.
 * 16 - DW: 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).

August

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

September

 * Publication of the second Doctor Who Annual.
 * 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 - DW: The Smugglers Episode 1 was first broadcast, marking the beginning of Season 4.
 * 17 - DW: The Smugglers Episode 2 was first broadcast.
 * 24 - DW: The Smugglers Episode 3 was first broadcast.

October

 * 01 - DW: The Smugglers Episode 4 was first broadcast.
 * 08 - DW: The Tenth Planet Episode 1 was first broadcast, marking the first appearance of the Cybermen.
 * Episode 4 of DW: 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).
 * Camille Coduri who played Jackie Tyler in series 1, 2 and (as a one off appearance) 4 of the BBC Wales-produced Doctor Who was born in Wandsworth London.


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


 * 29 - DW: 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 - DW: The Power of the Daleks Episode 1 was first broadcast. Patrick Troughton's first full episode as the Second Doctor, although William Hartnell briefly appears as a mirror reflection.
 * 12 - DW: The Power of the Daleks Episode 2 was first broadcast.
 * 19 - DW: The Power of the Daleks Episode 3 was first broadcast.
 * 26 - DW: The Power of the Daleks Episode 4 was first broadcast.

December

 * 03 - DW: The Power of the Daleks Episode 5 was first broadcast.
 * 10 - DW: The Power of the Daleks Episode 6 was first broadcast.
 * 12 - The BBC Audience Research Dept. files an Audience Research Report on DW: 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 - DW: The Highlanders Episode 1 was first broadcast. Frazer Hines debuted as new companion Jamie McCrimmon.
 * 24 - DW: The Highlanders Episode 2 was first broadcast.
 * 31 - DW: 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. (Presumably published prior to October as it features 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.