Thanks for the explanation. I think I get it; the turn when a character spawns is in cdir_events_dilemma_option_junctions_tables. And that has to match the years in historical_characters_tables.
This would only affect very few users, so no haste. I'll see what I can do myself.
Edit: But what we'd want to change to convert this to another tpy is the turn the character spawns in cdir_events_dilemma_option_junctions_tables, not the year, right? We want him in the same year window as before, but that is another turn now. So our 476 478 character should spawn in turn 2 instead of 8, if converting to 1 tpy.