We are already in the future. In a future. A high-tech environment, in many ways different from every other earlier part of history. Of course, there were many possible futures, and we inhabit only one of them. Where are the moon bases, for example?
In Jo Walton's My Real Children Patricia Cowan lives in two futures, with two different pasts. The year is 2015, and she is old and confused. It's dementia, but it's also the weirdness and vertigo of two sets of memories of two very different lives. She has three children. Or she has four. There was a bomb over Europe. Or there wasn't.