Oh, I really love your idea! Making the birthday a Holiday, way cool. That way it rolls around, same day, every year. All one would have to do is make a mark on a list for each Sim, to keep track of their 'age, as it were. I'm learning so much in this thread.
Since I play an historic game, I have an unpublished blogpost with all the years, birthdays, important historical events and inventions. That makes it so much easier to keep track. The best part of making the birthday a holiday is that I remember all birthdays even if I play rotationally.
