Re: How Long are Dogs Puppies?

Source: http://www.gamerevolution.com/guides/355931-sims-4-age-pets-make-cats-dogs-older#E3AGoVlGk1Z2YbOP.99

The process to age up your animals is a bit different than it is for human Sims. You'll have to get ahold of a new item introduced in this expansion: Dr. Magi-Heal's Medicine Craft-o-Matic. There are several places you can find the Craft-o-Matic. You can, of course, buy one for your house, but if you don't want to spend the Simoleans, you can always visit a vet clinic and use the one there.

To use the Dr. Magi-Heal's Medicine Craft-o-Matic to age up your pets in The Sims 4, you'll need to practice your Vet skill for a while. The Craft-o-Matic can produce items that you can use with your pets until you level up your skills you won't be able to make the thing you need to make your pet older.

Once you've practiced your Vet skill to a high enough level, you can head over to the Craft-o-Matic to start aging up your pet. You'll need to go to the "Craft" menu, then select "Treats," and then you'll see Age-Up Treat as a craftable item. Feed this to your pet, and they'll grow older by one level. So kittens will grow into adults, and adults will turn into to elders.