Life Cycle
"The Sims 3" prides itself on portraying a realistic life cycle. Characters must progress through seven developmental stages: Baby, Toddler, Child, Teenager, Young Adult, Adult and Elder. For a baby to become a child, it must first advance through the toddler stage. The precise time needed for a baby to become a child varies.
Timing
The game comes programmed with default settings determining how long each stage of the life cycle lasts. Without adjusting any of the game's settings, a baby will take three days to grow into a toddler. From there, it takes seven days for a toddler to become a child, bringing the total time necessary for a baby to grow into a child to be 10 days.
Settings
By editing the game's settings, you can adjust the length of a Sim character's entire life cycle or the length of time spent in a particular development stage. Click the "..." in the bottom left corner of the screen to access the game's options menu. Manipulate the menu's sliders to either increase or decrease the length of the Baby and the Toddler stages. You may also disable aging entirely if you would like to remain as a baby or toddler without becoming a child.
Gameplay
"The Sims 3" also offers several gameplay options for adjusting how fast or slow your characters age. Purchasing birthday cakes from the game's "Buy Mode" is an easy way to accelerate the life cycle. You can find the cakes listed in the "Parties" section when searching the "Buy by Funcrion" option. Once you've purchased a birthday cake, you can use it to skip up one life stage. It would take two birthday cakes to advance from baby to child. However, be careful, as advancing your children too quickly will hinder their development and prevent them from acquiring beneficial traits.