1978

March

 * 8 - The first episode of a radio play by Douglas Adams entitled The Hitchhiker's Guide to the Galaxy airs on BBC Radio, launching an entertainment franchise that would in the coming decades include novels, sequel radio plays, a TV series and a movie. The Doctor was a fan of this series and referenced it on several occasions. (DW: Ghost Light and The Christmas Invasion)

Unknown dates

 * The Doctor and Romana search for the third segment of the Key to Time on Earth, encountering the Ogri. (DW: The Stones of Blood)
 * Chris Parsons graduates from Cambridge and soon begins his post-graduate studies at St. Cedd's College. (DW: Shada)
 * The Doctor ships the newly built K-9 Mark III to Lavinia Smith's home in South Croydon as a gift for Sarah Jane Smith. However, the gift is not received by her until 18 December 1981. (KAC: A Girl's Best Friend) It is unknown whether he does this before or after meeting Romana, as he overides the randomiser many times in the next series, so he may have taken it to Sarah Jane then, or possibly after leaving Leela, as he may have dropped off K-9 Mark III while unpacking K-9 Mark II.
 * The Doctor brings Anji Kapoor and Fritter to a Hollywood bar, where they meet special effects photographer Ron von Arnim and later Noël Coward, who has arrived here from the 1960s using pinking shears given him by Iris Wildthyme which could cut through the fabric of space and time. (EDA: Mad Dogs and Englishmen)

January

 * 7 - DW: Underworld Part 1 is first broadcast.
 * 8 - Debut of All Creatures Great and Small on UK television. The series co-stars Peter Davison and launches him to stardom, leading to his being cast as the Fifth Doctor a few years later.
 * 14 - DW: Underworld Part 2 is first broadcast.
 * 19 - DWN: Doctor Who and the Face of Evil is first published.
 * 21 - DW: Underworld Part 3 is first broadcast.
 * 25 - Fred Ferris, who played the part of Bert Rowse in DW: Planet of Giants, dies.
 * 28 - DW: Underworld Part 4 is first broadcast.

February

 * 4 - DW: The Invasion of Time Part 1 is first broadcast.
 * 11 - DW: The Invasion of Time Part 2 is first broadcast.
 * 16 - Doctor Who Discovers: The Conquerors is first published.
 * 18 - DW: The Invasion of Time Part 3 is first broadcast.
 * 25 - DW: The Invasion of Time Part 4 is first broadcast.

March

 * 4 - DW: The Invasion of Time Part 5 is first broadcast.
 * 11 - DW: The Invasion of Time Part 6 is first broadcast, concluding Season 15. Louise Jameson leaves the series with this episode. Also final appearance of K-9 Mark I until the K-9 spinoff TV series of 2009.
 * 30 - DWN: Doctor Who and the Horror of Fang Rock is first published.

April

 * 20 - Doctor Who Discovers: Strange and Mysterious Creatures is first published. Although the Doctor Who Discovers series has been planned to run as many as 24 volumes, and at least three more books are in various stages of production, Target Books cancels the series after this release, citing poor sales.

May

 * 18 - DWN: Doctor Who and the Tomb of the Cybermen is first published.

June

 * 29 - DWN: Doctor Who and the Time Warrior is first published.

July

 * 14 - Jack Woolgar dies.
 * 20 - DWN: Doctor Who - Death to the Daleks is first published.

August

 * 29 - Tom Baker and Mary Tamm are interviewed on BBC Radio 2's Pete Murray's Open House.

September

 * Doctor Who Annual 1979 published.
 * Terry Nation's Dalek Annual 1979 published. Final release of the series.
 * 2 - DW: The Ribos Operation Part 1 is first broadcast. Mary Tamm joins as new companion Romana. Also first appearance of K-9 Mark II. This episode launches Season 16 (although it is promoted as the show's 15th anniversary), and the series' first season-long story arc, The Key to Time.
 * 9 - DW: The Ribos Operation Part 2 is first broadcast.
 * 16 - DW: The Ribos Operation Part 3 is first broadcast.
 * 23 - DW: The Ribos Operation Part 4 is first broadcast.
 * 30 - DW: The Pirate Planet Part 1 is first broadcast. First Doctor Who episode to be written by Douglas Adams (under a pseudonym).

October

 * 5 - May Warden, who played the aged Sara Kingdom in DW: The Daleks' Master Plan, dies.
 * 7 - DW: The Pirate Planet Part 2 is first broadcast.
 * 14 - DW: The Pirate Planet Part 3 is first broadcast.
 * 21 - DW: The Pirate Planet Part 4 is first broadcast.
 * 28 - DW: The Stones of Blood Part 1 is first broadcast, marking the start of the 100th TV story.

November

 * 04 - DW: The Stones of Blood Part 2 is first broadcast.
 * 11 - DW: The Stones of Blood Part 3 is first broadcast.
 * Vivienne Bennett, who played Queen Elizabeth I in DW: The Chase'', dies in London.
 * 16 - DWN: Doctor Who and the Android Invasion is first published.
 * 18 -DW:  The Stones of Blood Part 4 is first broadcast.
 * 22 - Tom Baker, Mary Tamm and Carole Ann Ford appear on the BBC's Nationwide to celebrate Doctor Who's 15th Anniversary.
 * 25 - DW: The Androids of Tara Part 1 is first broadcast.
 * 28 - André Morell, who played Marshal Gaspard de Saux-Tavannes in DW: The Massacre of St Bartholomew's Eve, dies in London.

December

 * During a break in production of DW: The Armageddon Factor, Mary Tamm, Tom Baker and John Leeson perform a brief skit for the BBC staff Christmas video in which the Doctor and Romana flirt with each other over a bottle of whiskey and K-9 tries to sing "We Wish You a Merry Christmas". Titled "Doug Who?", the skit circulates unofficially for years before being released in the Key to Time DVD set.
 * 2 - DW: The Androids of Tara Part 2 is first broadcast.
 * 7 - DWN: Doctor Who and the Sontaran Experiment is first published.
 * 09 - DW: The Androids of Tara Part 3 is first broadcast.
 * 16 - DW: The Androids of Tara Part 4 is first broadcast.
 * 23 - DW: The Power of Kroll Part 1 is first broadcast.
 * 30 - DW: The Power of Kroll Part 2 is first broadcast.

Unknown dates

 * American publisher Aeonian Press obtains the US publication rights to some of the Target Books releases, issuing them in limited distribution hardcovers. Among the books reissued in this format are DWN: Doctor Who and the Day of the Daleks and DWN: Doctor Who and the Giant Robot.
 * Eve Myles, who plays Gwen Cooper in Torchwood and Gwyneth in DW: The Unquiet Dead, is born in Ystradgynlais, Wales.
 * Tom Baker moonlights from Doctor Who to appear in another BBC series, Late Night Story, which featured Baker performing dramatic readings of horror stories. At least five episode, all between 13 and 15 minutes each, are recorded, but the series is never broadcast. Decades later, the five extant episodes are included as a bonus feature in the DVD box set of The Key to Time.