Okay, so. I trust Greta Gerwig, more or less. The trailer looks fun. I am 1,000% here for Kobna Holdbrook-Smith playing Frank.
But when the heck is Narnia: The Magician's Nephew supposed to be taking place? The costumes and hair are off by half a century.

Without time travel, I'm not sure how you get to the next chronological event happening half a lifetime later during the Pevensies's evacuation. If Frank drives a motorized cab, where does Strawberry/Fledge come from?
Mostly, though, simply why? What's wrong with setting the movie in the tail end of the Victorian or early Edwardian?
In those days, if you were a boy you had to wear a stiff Eton collar every day, and schools were usually nastier than now. But meals were nicer; and as for sweets, I won’t tell you how cheap and good they were, because it would only make your mouth water in vain. And in those days there lived in London a girl called Polly Plummer.