Open your Profile to access your personal settings:
Go to the Personal tab.
By clicking or tapping on the pencil next to Birth date, you can enter or change your birthdate
Here you can type in your Birth date:
Once you have added the right month, day and year you can click/tap Save to confirm or Cancel if you don't want to save the change.
How to change your birthday on the iPad
To change your birthdate go to Profile --> Account -->Personal and click edit near the Personal section.
Then tap on the line with Birth date and scroll up or down to the right date, month, and year.
Remember to save!