How far did the Whorl in Gene Wolfe’s Long/Short Sun books travel? The author leaves a few hints, although they are ultimately inconclusive. Fair warning: if you haven’t read the later novels in Wolfe’s Solar Cycle, this will be of little interest to you.
First, here’s a highly relevant passage from In Green’s Jungles. Silk/Horn discusses how long the Whorl’s journey was, and other characters try to determine how much time has elapsed on Urth since the unruined if rather decadent world remembered by one of the Whorl’s hibernating passengers:
“I only know that it has been about three hundred and fifty years since the Whorl left [Urth]. A bit more than three hundred and fifty, really–three hundred and fifty five, or some such figure.”
“There are seven thousand steps in a league…From what I’ve seen here, the streets are seventy or eighty double steps apart. Say a hundred to be safe. If Eco’s correct in his estimate, four leagues, they’ve been falling down for about two-thousand, five hundred years. If your son is, three-quarters of that should be one thousand, nine hundred, unless I’ve made an error”
[…]
“Old though these houses clearly are, I can’t believe they’re as old as that. No doubt the rate at which they’re abandoned was much higher at one time; but if we accept Cuoio’s estimate and the error is fifty percent, they’re still a thousand years old, roughly.”
So the Whorl traveled for about 350 years. However, it spent an unknown and possibly significant amount of time parked around the Short Sun — possibly as long as fifty years, about the time the other gods rebelled against Pas and Quetzal entered the Whorl. Somewhere between 1000 and 2500 years passed on Urth. Before I go further, I’d like to note something: Gene Wolfe’s Urth is nowhere near as ancient as Jack Vance’s Dying Earth, where the very mountains have worn down to hills.
Anyway: here’s The Relativistic Rocket, which explains in relatively simple terms how to calculate distance, velocity, and time in separate frames given acceleration and other values — which we have.