Turns out I don't actually have "date added" data--I was simply sorting on the collect id, which is just an integer and has no date information to go with it. Whoops. I've added the field, so it will work fine going forward, but I don't know how come up with convincing dates for all the existing collection items. Just to have SOMEthing, I've copied the "date bought" dates over into the "date added" fields. It's kind of lame, but at least it will make the sort dividers do something.
So, I'll mark this one as resolved for now until someone can come up with some interesting plan for guessing more accurate dates for all those old collection items.
