I was watching Blade Runner last night, for the first time in a number of years, and when I read the opening introduction text I felt a pang of regret when it placed the age of bellowing flames and unbreathable skies in 2019, in L.A. I regret it because it dates the film badly. It would have been so much better to never mention the date. A couple of changes in the script where 2017 could have been said “two years ago”, and the story would have been much the better. It’s a flaw in a vision of a dark future that still has things to say about genetic engineering.
I can understand the problem. I’ve made the mistake myself, several times. For example, in a Parking Spaces a short story published in the September 1985 issue of Analog, and maybe written a year earlier, I put 1988 as the date where engine control computers in cars developed a rudimentary intelligence. It was okay for a 1985 story that was quickly forgotten, but with just a little re-writing and put in Toyotas rather than Fords, it could find a whole new life.
Those early mistakes must have made an impression on me, because I made efforts to avoid explicit dates in nearly everything I write now. Just like movies use 555 phone numbers, nailing down a fixed point in time has consequences. Write for an age, not for a moment.