I do a very loose calculation of just how old my Sims are. I decided Erik was seventeen when I began this save. Being that it took three Terms at University for them to graduate, I calculated each term as one year. Which means, Erik was twenty years old when he and Kayleigh got married in 2279. Jamison came along in 2280. I've just now gotten around to making a chart for myself to help me keep track. Once all four seasons have completed (and my season's are set for 14 days), then everyone will 'age up'. Erik will become 37, since he's 36 currently. When the game ages them up, I shall have to work out just what age they are then.