Board Thread:Questions and Answers/@comment-27343779-20160405083111/@comment-1739368-20160405235126

I think what separates retcons from inaccuracies is consistency. Stuff like the date dio died is definitely a retcon because it's used afterwards regardless of version. The general rule of thumb is that if something is different, we reference later renditions of it to see if the same error is made; if so, it's likely the new canon. However, it's hard to say for the info where it's never mentioned again. This is typically why we'd enlist the use of the artbooks to set a standard, though I still don't own JoJoveller yet.

I like what the who wiki is doing, though I'm unsure how making everything canon would sit for a manga community.