Time and Infinite Gameplay

What I’m trying to do, and don’t even know how to get the aging bit done, is to create a rule/extension that grants NPCs and the PC a certain age at the beginning, and throughout the course of play, as all sorts of random things are going on, ages them further. My plan is for characters to marry, have children, those children to grow up and marry, and have children of their own, etc.

So even after designating units of time, how do I assign an age to each character, and make them grow older?

[code]A person has a number called age. The age of a person is usually 18.

To have a year pass:
repeat with the subject running through people:
increment the age of the subject.

Instead of examining a person: say “[The noun] [look] to be about [age of the noun in words] years old.”[/code]

Thank you!