There doesn’t really need to be a canon, because with the amount of Barry Allen-level time fuckery the show does, things can be erased or reinstated as required by the story. For example, the Last Great Time War involved the Time Lords and Daleks trying to erase each other from history, so everything from “before” that, essentially the entirety of Classic Who, can easily be said to have been retconned out of existence by the Time War. The lives of the First-through-Eighth Doctors might still have happened, but who knows what details have changed as a result of the Time War’s time fuckery. And in fact we know that near the end of the war, the retcons and erasures became so numerous that all of the defunct versions of the timeline themselves became another part of the war:
You weren’t there, in the final days of the War. You never saw what was born. But if the time lock’s broken then everything’s coming through. Not just the Daleks but the Skaro Degradations, the Horde of Travesties, the Nightmare Child, the Could’ve Been King with his army of Meanwhiles and Never-Weres, the War turned into hell! And that’s what you’ve opened, right above the Earth. Hell is descending!
If human history can be changed from “gravity” to “mavity” by accident, imagine the kinds of changes that took place when the Time Lords and Daleks were attacking each other’s histories on purpose.
Overall, very similar in concept to the Temporal Cold War seen in ST:Enterprise.
Famously, there is no canon. It’s all a tissue of expedience.
There doesn’t really need to be a canon, because with the amount of Barry Allen-level time fuckery the show does, things can be erased or reinstated as required by the story. For example, the Last Great Time War involved the Time Lords and Daleks trying to erase each other from history, so everything from “before” that, essentially the entirety of Classic Who, can easily be said to have been retconned out of existence by the Time War. The lives of the First-through-Eighth Doctors might still have happened, but who knows what details have changed as a result of the Time War’s time fuckery. And in fact we know that near the end of the war, the retcons and erasures became so numerous that all of the defunct versions of the timeline themselves became another part of the war:
If human history can be changed from “gravity” to “mavity” by accident, imagine the kinds of changes that took place when the Time Lords and Daleks were attacking each other’s histories on purpose.
Overall, very similar in concept to the Temporal Cold War seen in ST:Enterprise.