Copy, Right?

I was just in the bookstore (who does that any more?) looking at the Paul Hirsch book A Long Time Ago In A Cutting Room Far, Far Away.  It's about his life as an editor, most famously working on Star Wars (though it's hardly his only major film).

I noticed an interesting thing on the copyright page.  The book is copyrighted in 2020.  It's not quite 2020 yet, is it?  Since when can you copyright something in the future?  I thought you copyrighted something today so it couldn't be copied in the future?

Or let's put it another way.  Since it's copyrighted in 2020, and it's now 2019, it would seem the copyright isn't in effect yet.  So I can buy a copy and start making my own, selling as many as I want until New Year's Day.

And I don't want to hear Hirsch complain.  He had his chance, deciding nothing is copyrighted until next year.  He shot first.