UNIT dating controversy

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 — 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 is easy to grasp. Mawdryn Undead tells viewers that the Brigadier retired from UNIT in 1976. However, the events of The Invasion, the first story in which UNIT properly appears, approximately occurred in 1979. Thus, the UNIT dating controversy is, broadly speaking, an attempt to understand how the Brigadier could have retired from UNIT before UNIT even existed.

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 ^{[The UNIT Dating Conundrum [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. Consequently, the biggest period of UNIT involvement, the Third Doctor's era, has only comparatively mild contributions to the dating controversy.

Digging deeper

No television story actually featuring UNIT gives a clear year. Day of the Daleks comes close. It implies at one point that Jo Grant had just said the year, but Terrance Dicks was keen to keep the dating deliberately vague. The problem, which arguably should be called "the Brigadier dating controversy", exists primarily because of two appearances of Alistair Gordon Lethbridge-Stewart when he wasn't employed by UNIT.

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, Professor Edward 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 "forty years ago", tacitly setting The Web of Fear approximately in 1975. In a later adventure, 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 they briefly revisit the year. Since she 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. It's not particularly clear what to make of the statement. One possibility given by The UNIT Dating Conundrum is that the entire lot of UNIT stories from Spearhead from Space to The Seeds of Doom (where the Brigadier is still in UNIT but away in Geneva) happens from 1979 to 1980; if Sarah is speaking of her "home time", i.e. the time she (and Harry Sullivan) left with the Doctor, that would imply Planet of the Spiders, Robot, and possibly Terror of the Zygons when Harry leaves the TARDIS, would take place in 1980.

Another possibility is that she may just be speaking imprecisely. Whatever the case, her statement is not a clear violation of the continuity established by The Web of Fear. It does, however, indicate that the following "contemporary" stories of The Android Invasion and The Hand of Fear would have to take place in or after 1980 as Sarah encounters Harry and leaves in the two stories, respectively. The Seeds of Doom does not necessarily have to fit here.

What breaks UNIT dating is Mawdryn Undead. This story firmly and explicitly has the Brig retiring from UNIT in 1976, the year The Seeds of Doom came out. 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.

Contradictory clues

There are many other details that confuse the picture.

Some stories feature calendars, but these can contradict one another. 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. (1972 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 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 two stories. However, by Invasion of the Dinosaurs and Robot the Cold War is over. In Battlefield, Brigadier Lethbridge-Stewart refers to "the King" in a near future, but this could be just a figure of speech as Lethbridge-Stewart is old enough to remember when there was last a male monarch on the throne.
Mao Tse-Tung is implied to be alive at the time of 1971's 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 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) disk 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, Britain had a Space Defence Station for alien attacks and space freighters (implying they're taking the freight somewhere) that could reach Jupiter.
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 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.
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); laser guns are in development in 1974's Robot and then used by UNIT in 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. 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 Death of the Doctor (aired 2010 and set around that time), UNIT have a moonbase and their own rockets; by the The Waters of Mars (aired 2009, set in 2059), humanity still hadn't perfected interstellar travel, a Mars base is a highly significant achievement, and Britain lacks a space programme at all.
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.)
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. 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 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.

Off-screen evidence

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

A document prepared during the making of The Invasion by director Douglas Camfield states that he assumed the story was set in 1976.
The Radio Times programme listing and a continuity announcement at the start of the original transmission of episode one of The Invasion state that the story takes place in 1975. Announcements and publicity material were normally produced by the series' production office, usually by the Script Editor.
In a pair of 1969 interviews, then-producer Derrick Sherwin and newly cast Doctor Jon Pertwee told the press that the series (and thus the UNIT stories) would be set in a near-future time when things such as space stations would have become reality, with Pertwee confirming this would be in the 1980s.
A recorded but unused line in 1971's The Claws of Axos discusses comets due in the period 1969-1975, strongly pointing to an early 1970s setting for the story. By this time Sherwin had moved on as producer.
The 1972 book The Making of Doctor Who, written by then-script editor Terrance Dicks and regular writer Malcolm Hulke, dates the 1970 story Spearhead from Space to 1970. However the second edition of 1976 (rewritten by Dicks alone, after he had stepped down as script editor) does not specify any date.
The 1974 novelisation Doctor Who and the Sea-Devils, which Malcolm Hulke based on his own The Sea Devils, refers to North Sea oil starting to be exploited in 1978, indicating an early 1980s setting for the story.
The 1981 Writers' Guide for the proposed series of K9 and Company stated that Sarah's travels with the Doctor (i.e. from The Time Warrior to The Hand of Fear) took place between 1973 and 1976.
The 1983 story Mawdryn Undead was originally written with a different former companion in mind (specifically, Ian Chesterton) and much has been made of how this generated the UNIT dating "mistake", though other early 1980s stories and the above mentioned guide support Mawdryn Undead's dating of the story.
The "official" in-universe UNIT website produced by the BBC for the 2005 series notes in its history section that UNIT was formed in 1968 in response to the "London Underground" incident (The Web of Fear), and in its news section that 25 January 2005 was the 35th anniversary of UNIT's involvement in "Project Waxwork" (the concluding episode of Spearhead from Space was broadcast on 24 January 1970). These would date the stories as being contemporaneous with their original broadcast. With a joking nod to the controversy over dating of the original stories, the site also notes that "[UNIT] quickly expanded, making our presence felt in a golden period that spanned the sixties, the seventies and, some would say, the eighties." This sentence became part of on-screen canon in 2007 when it was visible during a scene in The Lost Boy, an episode of The Sarah Jane Adventures.
According to on-screen production notes for the DVD release of The Time Warrior, a line was struck from the script during Linx's interrogation of Sarah in which she would have explicitly stated her year of origin as 1974.
The UNIT Dating Conundrum looked at the in-universe evidence for the dating of the UNIT stories. It drew the conclusion that there was no reasonable way to reconcile the statements from Mawdryn Undead to those in Third and Fourth Doctor UNIT stories.

Other media

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

The novelisation Doctor Who and the Carnival of Monsters by Terrance Dicks, published in 1977, has the Third Doctor and Jo Grant visiting what they initially believe to be a vessel in the year 1926; Jo states that this was fifty years before her time. The first chapter establishes the story taking place immediately after the events of The Three Doctors, therefore putting that adventure in 1976 (unless Jo was rounding her numbers, which still places it in the 1970s).
The 1993 radio play The Paradise of Death by early 1970s producer Barry Letts is set at the time of the later Third Doctor stories and appears to have a 1990s setting, most notably references to virtual reality. (In the 1994 novelised version, however, Letts limits these references.)
The sequel, 1996's The Ghosts of N-Space, which is set again around the last Third Doctor stories, sees the sighting of a comet which appears every "157 years" and which was last seen in "1818", making the year 1975.
Novels in the Virgin New Adventures and the Virgin Missing Adventures line written in the 1990s took the editorial view that the television stories were set some time in or around the 1970s and left it to individual authors to decide on dates. This resulted in a number of contradictions. Events in The Invasion have been variously dated to the late 1960s, mid 1970s and late 1970s. Battlefield was assumed to take place in 1997.
Transit states the Doctor's exile on Earth was five straight years in the 1970s, so this would span from either Action in Exile or Spearhead from Space to The Three Doctors.
Blood Heat places Spearhead from Space and Doctor Who and the Silurians in 1973.
Who Killed Kennedy, published in 1996, ties several televised stories to real-life 60s and 70s political events, like the electoral defeat of the Wilson government. In doing so, it has stories taking place a few months before they aired.
Millennial Rites states that "the aborted attempt to tap geothermal energy" (Inferno) and "the British Space Programme" took place in the nineteen-eighties.
In The Scales of Injustice the Pale Man's statement of how the UK could've helped America in Vietnam by sending over a War Machine seems to be in past tense, implying the story takes place after the Vietnam War, which ended in 1975.
The Dying Days has Mars Probe 13, the last British Mars mission, taking place in 1977. The story is set in 1997.
The 1998 BBC Past Doctor Adventures novel The Face of the Enemy, by David A. McIntee, suggests that Mawdryn Undead may take place in a parallel universe where the Brigadier retired in 1976.
It is stated in the 1999 Eighth Doctor Adventure Revolution Man by Paul Leonard, when Sam Jones was released from prison in 1967, there was a document containing the Brigadier's initials and the UNIT call sign, although both the Eighth Doctor and Sam knew that the Brigadier was still Colonel and UNIT didn't yet exist.
In the Eighth Doctor Adventure novels Interference - Book One and Interference - Book Two, also published in 1999, Sarah Jane Smith is uncertain whether her experiences with the Doctor and UNIT took 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.
In the Big Finish Productions audio play The Coup, released in 2004, now-General Sir Alistair Lethbridge-Stewart states that UNIT has been fighting alien invasions for forty years, and that he "put down" a Silurian base thirty years before (he is likely rounding up). There is no indication as to which year The Coup takes place but the following The Longest Night says ICIS's Captain Andrea Winnington born in the 1980s; this would place it in the late 2000s at the earliest.
The IDW Publishing comic The Forgotten, first published in 2008, shows the Third Doctor during his exile on Earth, dated 1972.
Jo and Iris Wildthyme confirm the former's time at UNIT as being in the 1970s in Find and Replace.
The Fourth Doctor audio dramas The Valley of Death and The Oseidon Adventure have the Brigadier in charge of UNIT (but absent) in 1979.
The IDW comic, Prisoners of Time, first published in 2013, places the Third Doctor and Sarah Jane segment in 1974. It also establishes the Cold War, or at least Great Britain being under constant threat of mutually assured destruction, as ongoing, and has the Whomobile, which first appeared in the 1974 TV story Invasion of the Dinosaurs, taken out of mothballs so it can quickly reach UNIT's seabase.
The 2013 Puffin eshort The Spear of Destiny states directly (not once, but multiple times) that the Third Doctor works for UNIT in the year 1973.

Reconciliation

Although the controversy may have reached the point where it can never be solved, either because references to the controversy would still be made on purpose or writers would not take into account how others have dated the stories, there may be possible ways to organize or solve pieces of the controversy, if not the whole.

One stems from Marc Platt's Downtime, where the Brigadier and UNIT are discussed:

'Colonel Alistair Gordon Lethbridge-Stewart figures largely in its setting up in the Seventies. He's a Brigadier by then with a remarkable 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

Apart from dating The Web of Fear to the Sixties (the back cover reads "1966"), Downtime matches the UNIT timeline of Colonel Lethbridge-Stewart setting up UNIT by 1979 (The Invasion) by which point he is a Brigadier. It is possible no "official" records of the Brigadier were kept as a means of protecting him (Find and Replace states there was a fear of enemies coming after personnel after they'd left UNIT). If this cover up is true, it is possible for Lethbridge-Stewart to begin setting up UNIT in 1975 (if that is when The Web of Fear takes place) and "retire" in 1976 as stated in Mawdryn Undead. The only problem that arises from this is why the Brigadier would lie to the Fifth Doctor about his retirement, or why the Fifth Doctor would not recognize the date, if the Third Doctor was ever aware of when his exile took place.

Another possibility exists in that some, if not all, people associated with UNIT had their memories either erased or altered in some way, as was shown in The Day of the Doctor. The Third Doctor even tried to replace Jo Grant's memory of him in Find and Replace as a way of protecting her, and as Day has established, companions have had their memories wiped, even if simply to make them forget visiting the Black Archive specifically. So just how many people have had their memories erased or altered is uncertain, but Day also established UNIT is willing to cohere, if not control, the Doctor. If his memory was altered, then it would explain the above problem of the Fifth Doctor and 1976.

Sources

Parkin, Lance, Doctor Who: A History of the Universe - From Before The Dawn of Time and Beyond The End of Eternity (London, UK: Virgin Publishing, 1996), ISBN 0-426-20471-9
Miles, Lawrence & Wood, Tat, About Time: The Unauthorized Guide to Doctor Who - 1970-1974, Seasons 7 to 11 (New Orleans, LA: Mad Norwegian Press, 2004), ISBN 0-9725959-2-9