Besides finally straightening out the timeline (mostly -- still a few more dates to assign in that department), last week I also finally got to work on the missing chapter -- the one I skipped over by accident, assuming it was going to happen a little further on... and then realizing that what I had just written actually occurred after that chapter.
And this is why I hadn't done the timeline yet -- sometimes it rearranges itself while I'm writing, and I have to go back later on and nail down the dates once I've written the draft.
Anyway, it feels good to be back to work on the novel, and the missing chapter is coming along smoothly. I'll have to do some tweaking in the chapters before and after it at some point to make it fit the chosen timeline, but I think I'll save that for the revision process.
Speaking of revisions, I have a big job ahead of me when I get around to finishing revisions on the first book: I noticed when making my timeline that it seems a little... empty compared to the novel I'm working on now. I think the plot is solid, but might need to be fleshed out a little more. As soon as I get done with the missing chapter, I'll go back to the first novel to do revisions, and we will see then what I think it still needs!