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)

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)

During the Time 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)

Historical disputes
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)

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 Civil War. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)

Behind the scenes

 * 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.