Why the 35th century?

Why did Rei and his Ark II arrive at Tabit in 3455, not 2800AD or 3600AD?

My guiding principle behind the book(s) was that anything that could be fact checked, would check out.

The Arks traveled at a top-end speed of 5% of the speed of light. So the theoretical journey from Earth to Tau Ceti should have taken 240 years. If they continued on at full speed to Tabit, it should have added in an additional 420 years to travel the 21 extra light years.

But the whole premise of the book is that the Ark II hit something, probably an asteroid, and caromed out of the Tau Ceti system at an odd angle, straight for Tabit. My further assumption was that the propulsion module was damaged and therefore they could only coast.

When you put those two items together, you come up with about 1400 years of total travel time. If you add that to the launch year of 2067, you get 3467 but I didn't want it to be exact so I cut back the trip by a few years.

The small difference doesn't matter. What does matter is that Rei ended way the hell from where he expected and an incredible amount of time had passed. And then he met Rome...