For instance, in my work in progress, my antagonist is 52, my protagonist 36, and my second lead 28. If my story take place in 2023, that means they were born in 1970, 1986, and 1994 respectively. For each of them, any date before those are closed books, experientially speaking. They have no memories of anything that came before.
Of course they have access to a wealth of historical information that they can draw on all the way back to the big bang, but they weren’t there at the big bang, and that makes a huge difference. I am 65 in 2023, which gives me a frame of reference which extends back further than my youngest character by nearly 40 years. When seeing the world through her eyes I must see it with one eye closed, so to speak.
And of course their years of birth are hopeless when imaging their frames. What do you remember from the year of your birth? Probably nothing. My first memory is from the age of 3, and a very imperfect memory it is. If we take an arbitrary age of say, ten, we are just beginning to come to grips with the world beyond the schoolyard gate.
So none of my characters are likely to remember a president before Reagan or a time before personal computers. My youngest character’s earliest memory is Y2k. She won’t really recall a time before Facebook. The U.S. will have been at war in Afghanistan most of her life. My protagonist would have had the word “Whitewater” burned into his brain at an impressionable age. He would never hear Carl Sagan or Tiny Tim—especially not on Johnny Carson.
None of them would know the USSR, Nixon, the Vietnam War, or the Beatles on a first-hand basis. All of them would have known Queen Elizabeth II and Cookie Monster.
It’s like Steely Dan’s complaint in the song “Hey, Nineteen,” in which an aging hipster laments of his teen-age date:Hey, nineteen,
That's 'Retha Franklin,
She don't remember the Queen of Soul.
(You do remember Steely Dan, don't you?)
We’re each speaking a different language, based on experience. Of course, this could be carried further, since no two people, even identical twins, have exactly the same set of experiences, or the same reactions to them. And we can define our characters as precisely (or as generally) as we think necessary. But each of us is caged, to some extent, by the frameset of our lives. That’s a good place for a writer to begin understanding his characters.