The Doctor's reality (Death Comes to Time)

In one version of reality, the Seventh Doctor became the "last of the friendly Time Lords" and ultimately seemingly sacrificed himself in a final stand near Stonehenge to defeat a rogue Time Lord known as Tannis. In his absence, Ace, who had undergone training with the Doctor's old friend Casmus, was officially made the new Time Lord by the Kingmaker (WC: Death Comes to Time) while the Minister, despite having lost his status as a Time Lord, continued to travel in the universe using the formula for doors. (AUDIO: The Broken World, et al.)

According to one account relevant to the Eighth Doctor's life, the Doctor's parents Ulysses and Penelope Gate knew that Tannis was a future threat to Gallifrey which the Doctor would play a key role in defeating; (PROSE: The Gallifrey Chronicles) another account dealing with this same version of the Eighth Doctor acknowledged the Canisian invasion as a recent event. (PROSE: Trading Futures)

When the Seventh Doctor invoked his power as a "God of the Fourth" to destroy Tannis and, seemingly, himself, Tannis desperately cried out that the Doctor's actions would "disrupt the course of time", which the Doctor did not deny. (WC: Death Comes to Time)

When exposed to anti-time, the Eighth Doctor of the positive-time universe saw an alternate reality where the Time Lords had "terrible mind powers", (AUDIO: Zagreus) matching the mysterious powers which, in this account, Time Lords were said to inherently possess as "God[s] of the Fourth", despite being sworn never to use them. (WC: Death Comes to Time)

The Dominie remembered several different pasts and futures, as well as multiple alternative presents, including ones where he travelled with "androids" (PROSE: The Choice) like Antimony. (WC: Death Comes to Time)

Behind the scenes
The place of Death Comes to Time in wider Doctor Who continuity was a subject of controversy from the moment it was first released due to its depiction of an apparent death of the Seventh Doctor incompatible with his death in San Francisco and subsequent regeneration into Paul McGann's Eighth Doctor in the 1996 Doctor Who TV movie.

In its section for the then-recent webcast, the Doctor Who website featured a tongue-in-cheek article which presented itself an "completely unauthorised" explanation of how Death Comes to Time fit into wider Doctor Who continuity. The article pointed out that nothing in the webcast actually contradicted any element of televised lore up to Season 26 of the TV series, despite the perceived radicalism of its depiction of Time Lords as secretly possessing "magical mind powers" they had never used before. Indeed, it could be read as consistent with Virgin Books' entire New Adventures line, so long as one assumed that the mission at the end of Lungbarrow was not actually the direct lead-in to the TV movie that it was written as, and that the Doctor instead wound up travelling with Ace again, joined by Antimony.

However, regarding the apparent death of the Seventh Doctor, the article theorised that Death Comes to Time was actually an aborted timeline: in using his Time Lord powers to slay Tannis, the Doctor "disrupted the course of time" (as Tannis himself said in dialogue), creating a paradox by averting his already-fixed future death in San Francisco. This paradox could be what destroyed Tannis and the Doctor both. The article further speculated that Ace's duties as a newly-minted Time Lord would involve reversing the damage this had done to the timeline, making the entire Death Comes to Time timeline self-resolving and linking back to conventional Doctor Who continuity. "Sylvester McCoy regenerat[ing] into Paul McGann in the TV Movie [was] the established order of things. But I think we can tell from Tannis's dialogue that the Doctor is altering his own future by destroying himself on Salisbury Plain ("But you'll disrupt the course of time… you'll die too."). And it's the paradox that he creates that he destroys himself with. Or, at the very least, he takes himself out of time. […] The TV Movie did happen. Paul McGann was the next regeneration of the Doctor. But time has now been changed by the Seventh Doctor on Salisbury plain. I would guess that putting things right is part of Ace's quest."

- "Emily B"

The BBC added a disclaimer that the page's "theories" were purely personal and could "[turn] out to be inaccurate, wrong or silly".

Indeed, other BBC-licensed stories went on to contradict this interpretation. Big Finish's Doctor Who 40th anniversary release Zagreus referenced most of the contemporary branches of DWU media, construing each as a separate but equally valid "alternate reality"; one of these, a "universe where Time Lords had terrible mind powers", was listed separately from the Eighth Doctors Adventures reality, entailing that Death Comes to Time was demarcated from other continuities by more than just the Seventh Doctor's apparent death at Salisbury. However, the framing of the Zagreus anti-time vision preempted the identification of any singular branch, whether Big Finish's positive-time universe or another, as the "regular continuity".

The BBC Eighth Doctor Adventures, on the other hand, treated the events of the webcast as an established part of the Doctor's timeline on several occasions, contiguous with the mainstream Eighth Doctor's. In Lance Parkin's BBC Eighth Doctor Adventures novel Trading Futures, the Canisian invasion which served as the climax of Death Comes to Time was referenced as a recent event. In Parkin's subsequent novel The Gallifrey Chronicles, the Doctor's defeat of Tannis was mentioned as one of his future deeds prophesied at the time of his birth, alongside the events of The Invasion of Time and The Ancestor Cell. The Gallifrey Chronicles also referenced the Minister of Chance as the "man with a bent nose", extending a prior reference to the Minister in Jonathan Morris's The Tomorrow Windows. If there was still any doubt about Parkin's views on the matter, his reference guide AHistory included Death Comes to Time not in the separate section accorded to Scream of the Shalka and Doctor Who Unbound but as a normal part of the Seventh Doctor's life, depicting the start of Ace's journey into becoming a Time Lord around the same time as Neverland and The Sirens of Time.