"Urist McAxemurderer was born in the year 1736."
...The hell? The year's only 1512!
Good point you raise. Though I would think it would have to be very abstract.
Example:
"Axemurder" was a human land in the far away lands of "Planecountries" from across the seas. "Axemurder" was a strange land where men allow women to sit at their feasts and the men were known to competely shave their heads. Axemurder were brutal rivials of "Soaktrees" an Elven settlement.
Anyway dates could still be included if abstracted again. Much like how we have a B.C./A.D. system.
In your example Urist Mcaxemurderer was born in -271, or 271 B.C. or what ever dorfs would have.It really makes more sense. It alludes that the races migrated to your lands rather than popping up out of thin air.
Edit: I think I made a pretty big mistake with those dates. Should show me for trying to think at 4am.
Lets try again: The land which mr axemurderer came from would have been formed in -271 atleast (or 271 B.C.). This makes the world 271 years older than my (the player's) world, so the dates would all match up.
Another edit: Should be -224 years. /facepalm