newborn: 0
infant: 1-2
child: 10-12
teen: 17-18
young adult: 20-30
adult: 40-50
elder: 62+
They seem to have boosted every life stage to the end of that stage, which is kind of sad. It seems like chunks of time are just missing.
Toddlers age straight up to pre-teens, and teens are nearly indistinguishable from adults, except they still go to school. They made the infants stage to give us back that bit of really learning to do things which used to be part of toddlers (they used to crawl until they learned to walk, etc), but an infants stage still leaves gaps. It's jarring to age up to the end of the next stage instead of the beginning. Hopefully in the next Sims version they can work on that.
