Although the Walt Disney Company has never attempted to define or enforce a unified canon for the Disney Comics universe, it is often felt that, at least as far as the Duckburg mythos is concerned, primacy should be given to the work of Carl Barks, as he created many of the characters and concepts essential to it (beginning with Scrooge McDuck himself). A Disney Duck Comics Canon centered on Barks was first codified by Jack L. Chalker in his 1978 book An Informal Biography of Scrooge McDuck.
The book was a formative influence on Keno Don Rosa, a noted Barks fan with outspokenly little regard for Scrooge stories by other writers (even, he humbly points out, himself). Rosa's conception of the Duck universe as he defined it in his stories thus comprised Barks's stories and his own, knitting together Barksian facts into coherent worldbuilding, though this forced him to blur a detail or two on occasion. He also eventually worked a few non-Barksian facts into his canon, such as the manner in which Scrooge McDuck earned his Number One Dime (originating in the Carl Fallberg-Tony Strobl tale Chairman of the Bored) or the characters of José Carioca and Panchito Pistoles (from The Three Caballeros).
One of the consequences of this definition of the Barks-Rosa Universe is that Don Rosa proposes the present day of Duckburg only spans the years in which Barks was active; he dodges the conundrum of characters' frozen ages altogether by setting all of his stories in the 1950's, regardless of when they were published.
A few stories of his broke this rule, such as The Starstruck Duck, for which reason he does not hold them to be canonical even to his own Barks-Rosa Universe. Due to the enormous success of Don Rosa's stories and the influence they have had on the Disney Comics scene, many stories by subsequent writers avoid going against "Barks-Rosa facts", although this link only goes one-way, Rosa remaining unwilling to accept other authors into this publicized headcanon of his. Nevertheless, this Wiki chooses to instead take a much broader view of Disney Comics canonicity, holding nearly all licensed works set in the Disney comics universe (and quite a few unlicensed ones) to be canonical to our vision of Donald Duck's world.