How do you find out how old your penguin is on Club Penguin?

Click on the question mark and it'll say your penguins age.

For example;

Your Penguin is 1313 Days Old.

the way to work out how old your penguin is, is to look on the blue bar where you can go to your igloo, write a message etc. if you look down there you will be able to see a 'settings' if you click on there you will be able to find out how old your penguin is.