The Sims 3/Ages

Aging
Sims are always aging in the Sims 3. On the lots and in the neighborhood. There are 7 stages of life in the Sims 3. Baby, Toddler, Child, Teen, Young Adult, Adult, and Elder. Each stage has a different number of days to complete that age. At the end of a stage, a Sim transitions into the next stage. To change the life span of a your Sims, you can go to Options in the game, click on Game Options and slide the Sim Life Span bar to the left or right. This will let you choose how long or short you want your Sims life span to be. All Sim on the lot are effected using this option. Below are the number of days in each stage of a Sims' Life.
 * Baby: 2 days
 * Toddler: 7 days
 * Child: 7 days
 * Teen: 14
 * Young Adult: 21 days
 * Adult: 21 days
 * Elder: 16 days

Age Transition
When a Sim transitions to the next stage of life you are given a 2 day warning. When a baby transitions to a toddler, you want to make sure the baby has had a positive experience in order to pick the first 2 traits of that Sim. If the baby Sim has had a negative experience, negative traits will be chosen. If the baby Sim has had a moderate experience, the Sim's traits will be randomly chosen. When a toddler transitions to a child and a child to a teen, the Sim picks up an additional trait. If the Sim is doing well in each stage of life, you will get to pick a new trait. If they are doing poorly, a trait will either be randomly picked or picked from a list of negative traits.
 * You can have a Sim buy a Birthday Cake from the grocery store and set the cake on the counter or a table. Click on the cake and choose "Blow Out Candles". You can then choose what Sim you want to blow out the candles and advance to the next stage of life.

Baby
Babies require a lot of care, but have fewer needs than other Sims. Parents who carry around their babies are limited to sitting on the couch or in a chair away from a table, using the phone, and any other interaction that doesn't require touching. A list of baby's needs are listed below:
 * Energy: Babies get tired quicker than other Sims. When a baby tires it can fall asleep, but not in the middle of an activity. Babies sleep in cribs, so it is a good idea to buy one either before or right after baby arrives. Babies sleep cycles aren't night-day like other Sims. Baby Sim's parents won't be getting much sleep at night, so it is probably best to hire a sitter from time to time so parent Sims can get some rest.
 * Hygiene: Babies relieve themselves in their diapers. This makes the baby Smelly and causes a negative "Disgusted" moodlet on other Sims. Click on Baby and choose the "Change Diaper" option to change baby's diaper. If the "Change Diaper" option isn't selected right away, baby's crying can wake up other Sims in the house.
 * Hunger: Babies need a lot of feeding. To feed baby click on baby and choose "Feed Baby".
 * You must tend to the baby or the baby will get lonely. If you neglect any Sim younger than a young adult, there is a strong chance the Social Worker might show up. The Social Worker will take away the neglected Sim.
 * Babies can only be left with Sims who are teens or older. Child Sims can't take care of babies. If all adult Sims need to leave the house, it is best to call a Babysitter to come over.

Baby Interactions

 * Change Diaper: Baby will smell and give a negative "Disgusted" moodlet to Sims that are around. Baby's Hygiene drops also. Click on Baby and choose "Change Diaper" to clean baby up.
 * Hold: Use Hold to pick up baby and carry him/her around and interact with him or her.
 * Put in Crib: When baby is sleepy you can put him/her in the crib for a nap.
 * Feed Baby: Select Feed Baby to give the baby a bottle when it is hungry.

Baby Socials

 * Snuggle: Snuggle with baby to bring up his/her Social need and to build a better relationship with baby.
 * Play With: Play with baby to bring up his/her Social need and build a better realtionship with baby.

Toddler
Babies grow up to be toddlers. Sim parents can teach toddlers to Walk, Talk, and use the Potty. These are 3 lessons that should be taught to a toddler before he/she ages into a child. Toddlers need attention like babies, so if they are fussing or crying, you should socialize with him/her.
 * Energy: Toddlers sleep more regularly than older Sims, and a little less than babies. Toddlers also sleep in a crib.
 * Fun: Toddlers can play with toys or with other Sims for fun. Buy toys and set them on the floor for toddlers to play with.
 * Hunger: You can feed a toddler in a high chair or give them a bottle while they are sitting on the floor. To feed a toddler actual food you need a food processor.
 * Hygiene: Toddlers will go to the bathroom in their diapers if they are not Potty Trained. If they go in their diapers, they will give the negative "Disgusted" moodlet to Sims around them. Click on the toddler to change it's diaper or play as the toddler and click on the potty if the toddler has been potty trained.

Child
Child Sims attend school during the day from 9AM - 3PM. Children can make friends and socialize. They can use the toy stove to cook muffins, or grab snacks and quick meals from the fridge. They can't cook full meals until they become teens. They can, however learn cooking skills by clicking on the toy stove and cooking there. They can't read cooking books or learn recipes until they are older. Children have curfew warnings letting them know it's time to get home, unless they are on a lot or at a Sim's house they were invited to.