
I think I'm in line with the three Highlanders above me.
I set an eorzean year for Franz's birth, and then struggle to recalculate his age if asked OOCly. IC, we don't even know if most common people know what year they were born. For this sake, I usually just say "he's about 40". Vague enough to not have to deal with actual details, but close enough to work for a character who doesn't actually know his birthday. He makes general assumptions on when it would need to be, based of life events he does remember.
I set an eorzean year for Franz's birth, and then struggle to recalculate his age if asked OOCly. IC, we don't even know if most common people know what year they were born. For this sake, I usually just say "he's about 40". Vague enough to not have to deal with actual details, but close enough to work for a character who doesn't actually know his birthday. He makes general assumptions on when it would need to be, based of life events he does remember.