The idea is based on a book I read last summer. Think of it like this: a random piece of the Earth's surface is removed, and this is repeated on many time periods. Then, in an alternate universe, all of the pieces are reassembled to recreate the Earth. The pieces still fit together perfectly, even though they come from many different time periods. Some adjacent pieces could have a difference as little as a few days or as much as a few thousand years. All of this happens instantaneously, so anyone on those pieces don't notice anything happening, and, at first, will not notice anything had happened. How, why, and by whom this is done will remain a mystery (at least, until the end of the story).