Originally Posted by American Maid
Yeah, you're right. How can Thor be part of the Norse pantheon (and in the book that Jane and Co. look through) if he isn't born until almost the end of the Viking Age? Same for Loki.
While that oversight might give them liberty to do so, I still don't think they should compound their error by straining continuity vis-a-vis Darcy/Hela, though.
Its a pity they didn't dial the relevant date back just a couple centuries, it would have closed the plot hole just fine. As is, I suspect its better to just not think about it too much.