Then they didn't have such a system. Authors merely wrote what they wanted. Nowadays, all of that material, if it doesn't fit, is somehow retconned, or, if it is unsalvagable, is completely thrown out. Though they usually don't throw completely things out, due to an author's hard work. For instance, they're even attemptuing to keep some of that weird Marvel Comics stuff from the 80's in continuity. And.. since it doesn't contradict anything, they have even kept the holiday special in continuity! Yay!
