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The UNIT dating controversy is a problem of retroactive continuity (retcon) which has attracted considerable interest from fans and professional Doctor Who writers alike. It has also been the subject of a 2|entertain DVD documentary, The UNIT Dating Conundrum, included in the special edition release of Day of the Daleks. It has even made its way back into DWU narratives. These have most prominently included a sly remark made by the Tenth Doctor in The Sontaran Stratagem and on-screen graphics seen in The Lost Boy — the latter of which was actually in of itself a reference to the short story UNIT History: Fighting the unknown — but writers in other media have occasionally referenced the controversy, or attempted to solve parts of it.

The essential problem[]

Though replete with additional nuance, the nub of the narrative problem stems from one serial. Mawdryn Undead tells viewers that Brigadier Alistair Gordon Lethbridge-Stewart retired from UNIT in 1976. However, the events of The Invasion, the first story in which UNIT properly appears, approximately occurred in 1979.[1] Therefore, the UNIT dating controversy is, broadly speaking, an attempt to understand how the Brigadier could have retired from UNIT before UNIT even existed.

It is worth noting that the original intention of Mawdryn Undead was for Ian Chesterton to return as a teacher. But as William Russell was committed elsewhere and unavailable, it was ultimately decided that the Brigadier would return.

Writer Ben Aaronovitch has notably opined that there is simply no way to retcon the problem.

There is nothing you can do about [Mawdryn Undead]. It's just stuffed. You just pretend it's taking place in an alternate universe . . .Ben Aaronovitch [src]

Terrance Dicks has said he deliberately avoided giving dates during his time as script editor precisely so he could avoid these sorts of continuity headaches.[2] Consequently, the biggest period of UNIT involvement, the Third Doctor's era, has only comparatively mild contributions to the dating controversy.

Digging deeper[]

The problem exists primarily because of two appearances of Alistair Gordon Lethbridge-Stewart, one when he was a colonel in the regular army, and another when he was a public school teacher.

The first was his debut story, The Web of Fear, when he was still a colonel in the regular British Army. Here, he meets the Second Doctor, Jamie, Victoria and crucially, Travers. Victoria says that they met Travers in 1935 in the Himalayas, which they did in The Abominable Snowmen. It is further revealed that 1935 was "over forty years ago", tacitly setting The Web of Fear approximately in 1975 if not after. In a later adventure battling the Cybermen, called The Invasion, the Second Doctor again encounters the newly-promoted Brigadier Lethbridge-Stewart. The Brigadier says their last meeting was "four years ago now", ostensibly putting The Invasion approximately in 1979.

Viewers got no dialogue with a firm year for the whole of the Third Doctor's era. In Pyramids of Mars, however, it is claimed several times that Sarah Jane Smith is from "1980", and she and the Fourth Doctor briefly revisit the year — albeit in an alternative future where the world has been devastated by Sutekh. Since Sarah was the Third Doctor's final companion, and spent a good deal of time at UNIT, this has some implication for the theoretical date of UNIT stories set in seasons 11 - 13.

Whatever the case, her statement is not a clear violation of the continuity established by The Web of Fear. What breaks UNIT dating is Mawdryn Undead. This story firmly and explicitly has the Brigadier retiring from UNIT in 1976, the year The Seeds of Doom was broadcast. The Fifth Doctor confirms that "a year later" from the retirement is 1977, which offers viewers no wiggle room whatsoever. Because it's flatly impossible to have the Brigadier retiring before he's even become the Brigadier, a fundamental discrepancy indisputably exists in televised Doctor Who narratives.

in the Legend of Ruby Sunday, Kate Stewart placed the Doctor time at unit in the 1970's.

Other dating problems[]

Other problems with the timeline exist.

  • Aside from the aforementioned problems with Mawdryn Undead, the story also tells viewers that Sergeant Benton left UNIT in 1979. This only adds to the overall UNIT confusion, since viewers saw him being quite actively employed by UNIT in 1979, during the events of The Invasion. Since viewers also see Benton come back after The Invasion, it's even harder to swallow this Mawdryn Undead line.
  • At the time of the Third Doctor's regeneration in Planet of the Spiders/Robot, Sarah has a UNIT pass which reads "4th April 1974".
  • The Sarah Jane Adventures story Whatever Happened to Sarah Jane? shows Sarah Jane Smith as a thirteen-year-old girl in 1964. That would imply that Sarah Jane met the Doctor in her early twenties (Elisabeth Sladen's real age at the time). Similarly, in Invasion of the Dinosaurs, Sarah explicitly states her age as being twenty-three. Though not a part of the original televised "UNIT dating controversy", The Sarah Jane Adventures deepened the problem.
    • Sarah's UNIT pass is backed up by The Sacrifice of Jo Grant which states that Jo joined UNIT in 1972. In Death of the Doctor, the Eleventh Doctor says Jo was "what, twenty one, twenty two?" when he last saw her, thus placing her departure in 1972 or 1973, "just before I arrived" as Sarah Jane states in the episode, therefore backing up Sarah's 1974 UNIT pass.
    • This is, however, contradicted by The Other Woman, which says Jo arrived in 1970 at the age of 19 and therefore departed in 1971 or 1972 if the Doctor's words are correct.
    • Furthermore, Genocide says Jo has been "on the UNIT books since 1971".
  • Jo says that 1926 is "about forty years" earlier than her own time. (TV: Carnival of Monsters) What exactly she means by "her own time" is ambiguous. If it means her present day, then the Third Doctor UNIT stories take place in the 1960s. On the other hand, if she's talking forty years from her birth, then her present day would be sixty-odd years later, since she's in her early twenties when with the Third Doctor. However, since she's only approximating — "about forty years" — it's difficult to draw any firm conclusions from her statement. The difficulties of her statement are made worse by the fact that one of her character traits is an ineptitude for maths and science. She could have simply gotten her sums wrong.
  • In A Girl's Best Friend, Lavinia Smith tells Sarah Jane that the crate containing K9 Mark III arrived in 1978. Other parts of the story specify that Sarah Jane has been back on Earth for some time and she was working on Earth when the box arrived. This would place the relevant UNIT stories in the mid-1970s at the very latest, assuming the Doctor got the time correct when leaving K9 Mark III for Sarah.
  • In the 2007 Sarah Jane Adventures story The Lost Boy, a page from Sarah Jane Smith's UNIT dossier is clearly legible on screen. In it the following sentence appears: "[UNIT] quickly expanded, making our presence felt in a golden period that spanned the sixties, the seventies, and, some would say, the eighties." This is copied from the short story UNIT History: Fighting the unknown, released on the U.N.I.T. tie-in website in 2005 as a "in-universe" history of UNIT.
    • While the short story did reference the UNIT dating controversy, other stories on the website actually contributed to the Aliens of London dating controversy, providing inconsistent dates that may have been the result of deliberate, in-universe disinformation.
  • The Grand Serpent's plot in Survivors of the Flux introduces multiple new issues to the UNIT dating controversy. It establishes the origins of UNIT as being in 1958 and declares Lethbridge-Stewart to be a Corporal in 1967 — which creates major issues with any account of both The Web of Fear, where he is a Colonel, many ranks above Corporal, and The Invasion, where he is a Brigadier. It also causes issues with The Power of Three dating controversy as well, declaring that UNIT was shut down by 'Prentis' in 2017.

Contradictory clues[]

There are many other details that confuse the picture.

The Invasion - timestamp photo
  • In The Invasion, Vaughn acquires a photo of the Second Doctor and Jamie from security cameras, which has what appears to be a timestamp at the bottom that reads "E091/5D/78".
  • Some stories feature calendars, but these can contradict one another. 1973's The Green Death features two such references: one calendar — that in the colliery office — says the story is set in February in a leap year when 29 February falls on a Sunday. (1976 is the only one in the 1960s-1990s) However, it is clearly mentioned in the dialogue that the mine has been out of action for a year. The other — at Global Chemicals — says April. In 1975's The Android Invasion, the calendar in the pub gives the date every day as "FRIDAY 6 JULY". In 1975, 6 July was a Sunday; the nearest years in which that date fell on a Friday were 1973, 1979, 1984 and 1990.
  • The Prime Minister in The Green Death, who is only ever seen obliquely, is named as "Jeremy", meaning Jeremy Thorpe of the Liberal Party, which jokingly implies he was going to win the 1974 general election. (The Liberals were a minority party). This would set the story in late 1974 at the earliest, a year after the story aired.
  • Where politics are concerned, the stories offer a picture very different from when they were transmitted. Jeremy Thorpe was Prime Minister in The Green Death, which he never was in real life. There is a female Prime Minister in 1975's Terror of the Zygons, four years before Margaret Thatcher attained the position; the BBC's website claims this Prime Minister is Shirley Williams, who was never even a party leader in real life. The United Nations is more interventionist than its 1970s real-life counterpart, whilst the Cold War at times is on the verge of turning into World War III in 1971's The Mind of Evil and 1972's Day of the Daleks. However, by 1974's Invasion of the Dinosaurs and 1974/1975's Robot the Cold War is over.
  • Mao Tse-Tung is implied to be alive at the time of The Mind of Evil, or is at least referred to by Fu Peng as "our Chairman". In real life, he died in 1976, which would date the story before that.
  • The stories don't usually try to predict future fashions or technology, except when it is central to the plot. The result is that the stories look very strongly like the 1970s. An exception is 1968's The Invasion, where the fashions deliberately don't jibe with then-current fashions, suggesting a near-future setting for that particular story.
  • In the 1970 serial The Ambassadors of Death, Sergeant Benton comments that the distress signal SOS was done away with "years ago." In the real world, the SOS code was replaced as the standard distress signal in 1999.
  • The road fund licence (tax) disc on the Doctor's roadster, Bessie, in Robot, is dated to expire in April 1975. All registration year letters on the number plates of fairly new cars in the programmes made in the early-to-mid 1970s are contemporaneous.
  • Two years before Sarah Jane Smith was travelling with the Fourth Doctor in the 1975 serial The Android Invasion, she had researched a story as a reporter about Britain's "Space Defence Station", which had also apparently been involved in the "first test of the XK-5 space freighter" that made it as far as Jupiter before vanishing. This implies a fairly futuristic space program.
  • On the occasions that money is mentioned, most amounts given correspond to those in use at the time. 1970's Doctor Who and the Silurians features pre-decimal currency, when a taxi driver asks the Right Honourable Edward Masters for "Seven and six", i.e. seven shillings and sixpence (37½p in decimal currency); while Sarah Jane Smith needs only two pence for a call from a public telephone box in 1976's The Seeds of Doom. In real life, the United Kingdom adopted decimal currency in 1971 and was subject to significant inflation. In Battlefield, which is set around 1997, Pat Rowlinson asks the Doctor and Ace for "five pounds" as the combined costs for a glass of water and a glass of lemonade.
  • The technology displayed on occasion is more advanced than reality. The United Kingdom has a fully functional space programme that sends missions to Mars and Jupiter (TV: The Ambassadors of Death, The Android Invasion); "disintegrator guns" are in development in 1974/1975's Robot and then "laser guns" are used by UNIT in 1976's The Seeds of Doom; many of the science establishments seen are engaged in extremely advanced research; and there are two artificial intelligences, the first created in the late 1960s. (TV: The War Machines, The Green Death) Most of this technology is not seen in episodes set in the 1980s and onwards. 1968's The Invasion has videophones being used at International Electromatics and by the Ministry of Defence's Major-General Rutlidge. In The Claws of Axos, aired three years later, there is a videophone conversation between Mr Chinn (presumably a high level Ministry of Defence civil servant) and the British Defence Minister. The characters appear to be using standard technology.
  • Britain has a seventh manned Mars mission and an astronaut corps by the time of The Ambassadors of Death, without a mention of one in previous Earth-set stories. Who Killed Kennedy attributes to cyber-technology recovered after The Invasion but this still means Britain ran seven missions between The Invasion and The Ambassadors of Death; General Carrington was a Mars astronaut in the past and it's implied some time has passed. The Android Invasion says that two years ago, there was a British mission to Jupiter. Both Sarah Jane Smith and Jo Grant both believe that interstellar travel was close to being developed at separate times (Invasion of the Dinosaurs and Colony in Space respectively). The later Remembrance of the Daleks establishes the British Rocket Group operating in 1963; The Dying Days has the Mars Probe series go up to thirteen probes by the late 70s and a fourteenth Mars Probe sent in 1997. However, by the time of The Christmas Invasion (aired 2005 and set in 2006), the British government is boasting about sending an unmanned satellite; in Warriors of Kudlak (aired 2007 and set an undisclosed amount of time after The Christmas Invasion), Sarah Jane says the teenager Lance Metcalf might want to become an astronaut and the first human man on Mars; in Death of the Doctor (aired 2010 and set around that time), UNIT have a moonbase and their own rockets; by The Waters of Mars (aired 2009, set in 2059), humanity still hadn't perfected interstellar travel and wouldn't for about thirty years, a Mars base established the previous year is a highly significant achievement, and Britain lacks a space programme at all. The Tenth Doctor goes as far as to say Bowie Base One — the first off-world base of its kind — is made up of the "very first humans on Mars", though this is complicated by a claim in an on-screen obituary in the episode which states that a three person team, including the base's commander Adelaide Brooke, landed on Mars when Adelaide was 42 years old, in 2041.
  • The BBC has a third channel, BBC3, in 1971's The Dæmons. In 1971 the BBC had only two channels (though they aspired to launch a third channel in subsequent years). (The actual BBC Three, a digital television channel, was launched in 2003.)
  • The Seventh Doctor asks Ace (a native of 1987) about the "Yeti in the Underground" and the "Zygon Gambit", meaning if Terror of the Zygons takes place in the 1980s, it's before 1988.
  • Battlefield (made in 1989) is set in an unspecified near future. The Brigadier has retired from teaching for a few years; he is not many years older than he was in Mawdryn Undead. He's now married, when he lived alone in Mawdryn Undead. Major Husak is from Czechoslovakia, rather than the Czech Republic or Slovakia, but there are also five pound coins and the Brigadier refers to "the King".
  • In The Sound of Drums, President Arthur Winters tells the Saxon Master that first contact policy that places UNIT in control was decided by the Security Council in 1968, implying UNIT was already active in that year.
  • In The Sontaran Stratagem, the Doctor says he worked for UNIT in "the 1970s, or was it the '80s?" — a reference to this controversy.
  • The Fifth Doctor likewise referenced the controversy in the audio story The Gathering, when he requests that Alan Fitzgerald not ask him when he was employed by UNIT.
  • The Brigadier appears in Enemy of the Bane, an episode dated as occurring around the year 2009 (based upon its setting within the recent Whoniverse); however, the Brigadier is considerably aged for someone who, based on other evidence, would have been active in UNIT only twenty years earlier. In particular, the Brigadier is considerably older than he was in Battlefield, yet stories contemporaneous to Enemy of the Bane establish that the Queen is still on the throne.
  • In The Day of the Doctor, Kate Stewart asks for one of her father's files; she says it may be filed under the 70s or the 80s "depending on the dating protocol", a clear reference to the UNIT dating controversy. No more is said on screen to explain this so-called protocol or how it works.
  • In Clara Oswald and the School of Death, the Twelfth Doctor dates the resurfacing of the Sea Devils in The Sea Devils to "1972... or 1982, it gets foggy... your time."
  • In The Sinestran Kill, set in 1978, Scott Neilson knows of the Doctor as an employee of UNIT from his five years in Special Branch.
  • In the 1975 TV story Terror of the Zygons, the Brigadier mentions the Navy are "sending some frigates from Chatham" to an underwater object (the Skarasen). In the real world, Chatham Dockyard closed in 1982.
  • In The Zygon Invasion, Kate Stewart makes a reference to "an attempted Zygon invasion before, in the '70s, '80s," likely referring to the 1975 TV story Terror of the Zygons, and also meaning that that story and later stories' placements are not definitively in the 1980s.

Off-screen evidence[]

Published books, contemporary interviews, publicity material and behind the scenes documents all point to uncertainty amongst the production team as well.

Other media[]

Stories in other media have also offered dates for the UNIT stories but have had little success in producing a clear answer:


Virgin Books[]

BBC Books[]


Big Finish[]


Solving the controversy[]

While many stories have tried to give specific dates to a serial, very few have offered an overall answer to the problem.

In Marc Platt's novelisation of Downtime, Christopher Rice states that there were no "official" records of the Brigadier while discussing UNIT:

'Colonel Alastair Gordon Lethbridge-Stewart figures largely in its setting up in the Seventies. He's a Brigadier by then with a remarkable active service record.' He leant forward slightly. 'And then he vanishes.'

'You must have known him during your time at UNIT,' said Miss Waterfield.

Sarah shook her head wearily. 'Sorry to disappoint you, but I'm just a journalist.'

'With no "official" records of him, you could easily imagine Lethbridge-Stewart was dead,' continued Christopher.

The Vice Chancellor half turned to him. 'UNIT looks after its own.' Page 100 [src]

The notion of UNIT personnel being protected later comes up in the audio Find and Replace, where it's stated there was a fear of enemies coming after personnel after they'd left UNIT. In that story the Third Doctor attempted to alter Jo Grant's memories as a way of protecting her.

The Virgin New Adventure The Dimension Riders introduces the concept of crystallized time, where alterations to the timeline usually manifested as small things like dates changing their days, which could account for such discrepancies between the DWU and the real world.

In the Eighth Doctor Adventure novels Interference - Book One and Interference - Book Two, published in 1999, Sarah Jane Smith is uncertain whether her experiences with the Doctor and UNIT take place in the seventies or the eighties. At the end of the "What Happened on Earth" portion of the second novel, she asks the Doctor about this, and he replies "Temporal slippage. ... My fault, I'm afraid. I think it's currently the 1970s, but —" and is interrupted by Sam Jones.

This solution was later reinforced by The Enfolded Time, where the Accord explains that the Doctor's regular visits to Earth from 1969 to 1989 in his faulty TARDIS disrupted the planet's timeline, enfolding time in on itself so that twenty years occurred over a ten-year period and the Accord is trying to repair the damage to strengthen it before a forthcoming war. The obvious mix around of some of this history is then handled by the dating protocols.

In The Split Infinitive, the '60s and '70s are said to be being dragged together when a group of Rocket Men are trapped in the respective eras, crunching the years down. Ace explains that this will have caused UNIT's timeline to be scrambled due to their association with the Doctor and other time-travellers, and the Seventh Doctor explicitly references the Brigadier retiring in the '70s and working in the '80s as a symptom of this damage.



  1. The Radio Times programme listing for The Invasion episode one sets the story even earlier, as the synopsis begins: "The Tardis brings Dr. Who, Jamie and Zoe back to England, but England about 1975." (original published text)
  2. [[The UNIT Dating Conundrum (documentary)|]]
  3. https://www.bbc.co.uk/doctorwho/classic/episodeguide/datingunit.shtml