The Scrooge McDuck Wiki starts from the perspective that everything is canonical. This is, of course, not literally true, but it takes extraordinary evidence for us to declare something non-canonical. Narrative conflicts are not, usually, extraordinary evidence.
Therefore, you must be prepared to handle conflict in the writing of in-universe pages. If possible, create a theory that allows the events to fit together. If not, use the Broadstrokes Principle as detailed further below.
If you still cannot fit the two canonical stories together, we recommend you use language like: “According to most accounts, Scrooge McDuck only came to Duckburg in 1902, whilst another held that he had come there much earlier, having lived there 70 years by 1954.”
The Broadstrokes Principle is a way of resolving
continuity issues that no amounts of theorizing
can explain away, try as we might, if these issues are relatively minor to the plot of the story from which they stem.
In its simplest form, the Broadstrokes attitude refers to assuming that two contradictory stories or facts are both canon in the abstract, but the specific details of either may not be quite as they were depicted in the stories. For example, Life and Times of Scrooge McDuck is ostensibly in continuity with the various Carl Barks stories on which it is based, but blurs a few details, such as the date of the event of Voodoo Hoodoo. We thus assume that the events of Voodoo Hoodoo still “happened”, except that the few lines of dialogue in question were “actually” somewhat different and fit the rest of canon.
This is also how we treat stories like Bedknobs and Broomsticks: stories that have ample evidence for their canonicity, but seem to take place in worlds where anthropomorphic animals are seen as mere fantasy. Per the Principle, we assume that the plot still happened, but the dialogue about anthropomorphic animals did not take place in the form presented.