Daleks' timeline

By several accounts, the Dalek species had a unique timeline which was heavily interfered with on multiple occasions from conflicting accounts of their origins to being further complicated by the Last Great Time War. (TV: Genesis of the Daleks, PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe, Dalek Combat Training Manual)

Nature
The Eighth Doctor found Dalek history a difficult thing to remember because it was always changing. (PROSE: Alien Bodies) A member of Faction Paradox thought that this was because the Doctor "tricked the Dalek Empire into tangling their timeline so bad that their history collapsed under the weight of the paradoxes". (PROSE: Unnatural History) The narrator of The Dalek Conquests noted that writing a precise chronological account of Dalek history was made very difficult by the fact that the Daleks possessed time travel. (AUDIO: The Dalek Conquests) Historians who studied the Daleks noted the Daleks themselves often dipped back into their own past in their attempts to rewrite past failures, (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe) and not even the Time Lords could organise all accounts of Dalek history together. (PROSE: Dalek Combat Training Manual) The Tenth Doctor reflected that "Dalek history was confusing enough before the Time War." (PROSE: Prisoner of the Daleks)

Witnessing a projection of what Gallifrey would be like under anti-time, the Eighth Doctor watched as a twisted version of Romana II, under the title of Imperiatrix, rejected the Dalek Emperor's plea for help. Despite the Emperor claiming that the Time Lords' "continuity" could not survive without the Daleks, the projection ended with Romana declaring its species enemies of the Time Lords and having the Emperor's entire fleet destroyed, wiping out the Daleks. This projection held that the Web of Time would fall into shreds. (AUDIO: Neverland)

During the Time War, the Dalek Time Strategist studied the timelines and came to understand that the Daleks' timeline was "impossibly entangled" with the Doctor's timeline as result of their numerous confrontations, going beyond even into the post-Time War universe. As a result, the Strategist found that the Doctor could not be easily eliminated without consequences for Dalek history, with the Eighth Doctor observing that the Dalek was hesitant to kill him lest it interfere with its plans to kill him. (AUDIO: Restoration of the Daleks)

Also during the war, the Time Lords scrutinised Dalek history with the assistance of the Doctor's memories, the results of which were recorded in the Dalek Combat Training Manual. To that end, they ordered notable incidents into timelines of both Dalek history and of Dalek activity in the linear history of the universe. Furthering their knowledge, the Time Lords used the Matrix to project encounters, then thought to be theoretical, between the Doctor and the Daleks in the post-Time War universe. In addition to the "ratified accounts", there was also a vast amount of additional information gathered from a variety of sources, the validity of which was disputed by scholars as some accounts contradicted what was known about the Daleks from "more authoritative sources". It was a matter of opinion whether these were apocryphal or evidence of Dalek activity in parallel dimensions. Such "anomalies" in Dalek history included alternative accounts of the Thal-Dalek battle, a "very different origin story" for the Daleks and their Emperor which contradicted the known record of Davros, the Space Security Service's conflict with the Daleks, an account from the planet Strellin, the Dalek Time Controller and Dalek Time Strategist and the activity of the Dalek Time Squad. (PROSE: Dalek Combat Training Manual)

The history of the Daleks was also studied by human historians in the post-Time War universe, following the Siege of Trenzalore. These historians were aware that the Time War, which was itself contained within its own timeline, had irrevocably changed the history of the universe, divided between the pre-Time War universe and the post-Time War universe. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)

Established by Dalek survivors following the Time War, the New Dalek Paradigm successfully returned to their "own time", which the Eleventh Doctor knew to be in the future relative to 1941. (TV: Victory of the Daleks) In their record of Dalek activity in linear history, the Time Lords indicated that the New Dalek Paradigm was based in the "far future" following the pre-Time War Hand of Omega Incident, which itself followed the 47th century Necros Incident. (PROSE: Dalek Combat Training Manual) Some observers suggested that the annihilation of the Parliament of the Daleks at the end of the Siege of Trenzalore was the "Final End" of the Daleks, though historians were aware that Skaro remained behind an invisible shield. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)

A damaged New Paradigm Supreme Dalek was found by historians in a Renegade Dalek base on Thule, leading to speculation that the later faction had interfered in the Imperial-Renegade Dalek Civil War. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)

Dead Planet Incident
Though the residents of the Dalek City in the Dead Planet Incident were understood to be primitive Dalek War Machines, some Time Lord theorists suggested that the First Doctor's encounter occurred near the end of the Dalek timeline, and that the Daleks had lost some of their earlier mobility, with some unknown event in Dalek history forcing them to abandon their empire and return to Skaro. (PROSE: Dalek Combat Training Manual)

Age of Universal Peace
Accounts of the Age of Universal Peace following the 2400s Dalek invasion of the solar system lasting "two hundred years" until the beginning of a 27th century Dalek invasion, (COMIC: The Mechanical Planet) conflicted with accounts of the Dalek Wars, specifically the Second Dalek War which was fought throughout much of the 26th century. (TV: Frontier in Space, PROSE: Love and War, Prisoner of the Daleks, et al.) The narrator of The Dalek Conquests noted that writing a precise chronological account of Dalek history was made very difficult by the fact that the Daleks possessed time travel. (AUDIO: The Dalek Conquests) Indeed, it was known that Daleks with time travel native to the 40th century attempted to go back in time to launch an invasion of Earth in 2415 but the Golden Emperor's time machine was faulty and he ended up in 1415 during the Battle of Agincourt. Without their leader the invasion was a failure and the remaining Daleks quickly surrendered. (COMIC: The Secret of the Emperor)

Vulcan Incident
In the Vulcan Incident, the Second Doctor thwarted an attack on Vulcan, a 21st century human colony, by Daleks which had crashed on the planet in a space capsule. (TV: The Power of the Daleks) Human historians indicated that this factory ship was from the early Dalek Empire. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe) Another account indicated that it had fallen through time during the renewed civil war between the Daleks loyal to the Dalek Prime and those loyal to Davros, (PROSE: War of the Daleks) whilst the Time Lords' indicated that the ship was from some point following the Time Destructor Incident of 4000 but before Operation Human Factor. (PROSE: Dalek Combat Training Manual)

Mechonoid Incident
Recognising the First Doctor's role in the thwarting of the 2150s Dalek invasion of Earth, the Daleks dispatched Pursuer-Daleks in a time machine to ill-fated execution attempt. (TV: The Chase) The Time Lords indicated that the deployment of the time machine occurred relatively shortly following the liberation of Earth, within the 22nd century. (PROSE: Dalek Combat Training Manual) Human historians, however, suggested that it occurred late in the Dalek Wars. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)

The Space Museum
A Dalek casing was found by the First Doctor in the Moroks' Space Museum on Xeros. (TV: The Space Museum) Several theories were proposed as to how the Moroks had acquired a Dalek War Machine casing for their museum. Historians who studied the Dalek race theorised that the casing might have been a discarded piece of Dalek refuse that the Moroks had claimed or had once belonged to a Scout Dalek that had been overpowered. (PROSE: The Whoniverse) The Time Lords believed that the Dalek had been one of the combatants of the Thal-Dalek battle, its inert shell claimed by Morok scouts who visited Skaro. Their record of Dalek activity indicated that the casing was exhibited in the museum in the 22nd century, prior to the 2150s Dalek invasion of Earth. (PROSE: Dalek Combat Training Manual) According to another account in the Dalek Survival Guide, this Dalek was in fact one of the Pursuer-Daleks who had left their fake Time-Space Visualiser on Xeros for the Doctor to acquire, but was killed and displayed by the museum's curator for not paying admission. (PROSE: Dalek Survival Guide) The remaining Pursuer-Daleks were slatted silver Daleks supported by dark-domed War Machines. (TV: The Chase)

Operation Human Factor
One account dated Operation Human Factor and the ensuing Dalek Civil War as taking place over 1000 years into a Great War which began with the Dalek defeat in the Time Destructor Incident of 4000. (PROSE: The Evil of the Daleks) However, the Time Lords placed these events following the 41st century but before the recovery of Davros during the Dalek-Movellan War in the 46th century. (PROSE: Dalek Combat Training Manual) By one account, the Human Factor Incident and the prior Time Destructor Incident took place following the Dalek Civil War between the Supreme Dalek and Davros, who had created a new race of Daleks on Necros. (PROSE: The History of the Daleks) Most other accounts indicated that the civil war postdated these events. (TV: Remembrance of the Daleks, PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe, PROSE: Dalek Combat Training Manual)

The Gold Dalek
As human historians understood, the Gold Dalek that plotted Operation Divide and Conquer with went on to orchestrate the Time Paradox Incident. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe) However, the Time Lords indicated that Divide and Conquer followed the Time Paradox Incident. (PROSE: Dalek Combat Training Manual) Indeed, the Gold Dalek did not recongise the Third Doctor during this incident despite his role in defeating their plan with the Master. (TV: Day of the Daleks, Frontier in Space)

Davros before Necros
Human historians were aware of unverified claims that Davros, having survived the Duplicate Incident, came to be employed by Arnold Baynes, CEO of TransAllied, Inc. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe) By one account, this was indeed the case, with Davros being confronted by the Sixth Doctor. (AUDIO: Davros)

Trial of Davros
Human historians were aware of conflicting accounts as to the immediate aftermath of the Necros Incident, in which Davros was apprehended by Daleks loyal to the Supreme Dalek with the intent to have him stand trial on Skaro. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)

Civil War
Human historians also had no clear answer as to the immediate aftermath of the Shoreditch Incident and the destruction of Skaro, including the ultimate conclusion of the Imperial-Renegade Dalek Civil War and the circumstances of the eventual return of Skaro. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)

The Good Dalek
The Twelfth Doctor met Rusty in the Good Dalek Incident, as the bronze Daleks were opposed by the Combined Galactic Resistance. (TV: Into the Dalek) Human historians believed that this Dalek invasion of the galaxy was part of the Dalek Wars prior to the Time War. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe) However, the Time Lords indicated that it followed the Siege of Trenzalore. (PROSE: Dalek Combat Training Manual)

Behind the scenes

 * The Discontinuity Guide made the claim that, originally, Davros was killed and forgotten, and that the Fourth Doctor's interference with the creation of the Daleks created a new timeline where Davros survived, the Doctor's warnings about the Daleks having made Davros paranoid enough to activate a force field in his chair. As a result, whilst the Daleks originally had a solid, cohesive empire, always with one purpose, Davros' presence reduced them to "a mess of squabbling factions" which were "incapable of the unity needed to develop dimensionally transcendental time travel. Published before the Last Great Time War was established in Doctor Who lore, The Discontinuity Guide went on to claim that "whilst Davros lives the Daleks will remain disorganised, and will never become the threat that the Time Lords so feared."
 * The Dalek Handbook claims that the grey Daleks succeeded the silver Daleks as the drones following the Dalek Civil War, dated to the 41st century, and that their presence in the 26th century Operation Divide and Conquer and the Spiridon campaign was indicative of continued operations to overwrite history in the Daleks' favour, with the silver Daleks seen in the Exxilon Gambit being 27th century-native Daleks that had been subsumed into future Dalek forces. It is suggested that the Fourth Doctor's interference did create a new timeline, but how this changed known Dalek history remains uncertain.