How far back do you go when writing a fantasy? And I don't mean where you story begin, but when your universe begins.
My fantasy wip has a skeletal history for the country it's set in going back to when it was first colonized. Very skeletal. I haven't even laid out exact years. I figure it was about two hundred, but since the exact numbers aren't important to the story, it's just kinda handwaved as being generations ago. I haven't expanded beyond that. Granted, it's a smaller project. For my far-future sf one, I basically have it worked out from our present day to almost a thousand years in the future, which is the in-universe present day.
Around one thousand four hundred years at the moment, my main country being founded two hundred years ago, it's predecessor popping up eight hundred years again, and then six hundred years of world-altering events beforehand.
As far back as I need for anything important that might impact or set up the story. In a novel, there's not too much point in addressing history that's not going to matter in the story and setting, unless you're planning to incorporate it into a prequel or sequel. At best, I'll make vague mentions to certain pieces of information that might add some extra flavor, but never more than a few sentences. That being said if you're just using that info as a personal reference for world-building purposes, then go as far back as you want =)
Nice! I, myself, was inspired by the Silmarillion and by reading about Ronald Tolkien's life, so I took a gander at starting from the very beginning, a creation story, in a sense. Which have become very daunting because I approached the story as any other, that it needed to make sense. It really doesn't so much in the time of the gods, things sorta happen and even in the Silmarillion did Balrog, dragons, and other evil creatures appear with the explanation that they came from the depths and were creations of Melkor. I'm stuck on a certain aspect where I need a cataclysmic event to happen and force the people of my Universe to emigrate, not sure what the cause would be though... Some ancient evil festering in the underworld, I suppose. Still, I do want it to be more mysterious instead of outright Human vs Monsters situation.