One thing I’ve been curious about while reading these two books.
What does putting a date on them do to the narrative?
Many sci-fi/speculative fiction set their stories in the unspecified future. Maybe you can guess where it is, but it’s not specifically stated. Others do state it (a lot of mind 1900s sci-fi films set things in the 2000s because it was the nigh on impossible to imagine future.)
So Butler sets these books in the not too distant future (shout out to my fellow MST3K fans). So not too distant, that in the first book, it starts three years from now (but twenty years ahead of her).
What does that do to/for the book? Does it feel closer when she’s writing it (or if you read it when it came out). Does it impart a sense of urgency that an unspecified future imparts?
I don’t read a ton of sci-fi so I don’t really draw from a lot of examples.
Infinite Zombies 
I don’t have a great deal of sci-fi under my belt either, so I’m no subject matter expert. I guess my take is that setting it in a definite future timeline adds to the “hey, look, everything’s going to hell here and fast” urgency of it, which ties to the question that came up a few weeks ago about what purpose this sort of doom and gloom literature serves to begin with. There’s an immediacy, maybe — it’s not “hey, look, a sand planet in a very clearly distant future” but is more “wake up, we’re looking at your kids’ or grandkids’ future here.”
I’d say some of the effect of putting a date on a story depends on how much meaning the author is able to give that date, and what kind of story they’re trying to write. If the futurism and its predictions are the point, the date becomes very important, because that’s the bet the author’s making. (Or you can be William Gibson, if you’re lucky, and understand where we’re already currently living in the future.)
My short-reflection thought on it is that giving an identifiable date give the author a knob to twist in calibrating how much the story partakes of myth. Dune is 25,000-some years in the future because it’s supposed to feel mythic; same with Star Wars being “a long time ago,” despite the fact that much of its technology remains unrealized in our lives. In those cases—and to a certain extent the ones you mention in the post, Paul, where they’re in the 2000s, because oooooooh—the date tells you specifically that you’re not supposed to bother connecting your own world to the world of the story. (That doesn’t mean you can’t read parallels in, but that they’re more likely to be parallels to things from history rather than things from the author’s present.)
But a date can also foreclose that mythic interpretation and the comfort that it can bring (through the distance it imposes between reader and story). That’s more of what the Earthseed books are doing, particularly (I think) given Butler’s focus on minority experiences: telling readers that this isn’t some distant past, or some future you’ll never see, but a plausible extrapolation of right now.
Or, if you like: What Daryl said, mostly. 🙂
That all makes sense. It’s like putting a date on it says to watch your own ass, reader.