History is history. If you were born 31 years ago, you have to trust in other people that X is recent, and X was a really big deal and so on.
50 years (class rock), 80 years (depression world war II), 100 years (world war I), 150 years (civil war), 240 years (revolutionary war), 400 years (beginning of the scientific revolution), ancient rome 1700+ years ago.
The only difference is the 50 years ago is lots more people agree that X is a big deal for they lived it, but once you start getting the 80 to 100 years ago, but especially the 100 years ago you no longer having living memory of other people and it is now just mythology and books.
The Wheel of Time turns, and Ages come and pass, leaving memories that become legend. Legend fades to myth, and even myth is long forgotten when the Age that gave it birth comes again.
Now if you did not live that history, then that time is amorphous. I repeat this.
You can trust in the stories people older than you tell, but it is still amorphous, but you have some forms of anchors with the stories of other people when they tell about their living memory. But it is still their memory and not my memory.
And sometimes one person's living memory contradicts another person's living memory. Mookie have you ever heard of third culture kids? (Military brats who lived oversees and so on) Well I have some aspects of third culture kids for I throughout my own personal experience quickly learned that my adults and elders often did not agree about what happened in their generation and that there is something called point of view. Some kids start learning about PoV after the age of reason (roughly age of 7), but when a child learns about PoV and gets it at a far younger age well it does things to a person psyche. Not necessarily bad things or good things, but they view the world differently than other people their age.
...sigh...
My point is Time that does not involve you, just like Space that does not involve you lacks the same type of temporal anchors in your long term memory as time and space that you physically participated in. It feels adrift, like a world of a night without stars or moons a world of a void with floating lamps but no lamp posts for you to touch. A drunk uses the lamppost to help steady themselves and to create a sensory feeling of bearings and internal logic. Another point of a lamppost is to illuminate as a light bringer and to show you the truth. But in a world with floating lamps and no lamp posts well that seems like a world of a dream, and you feel confident when your feet are steady but when your feet are not steady the world of the night yet surround with floating lamps seems surreal and like a dream.