Does your profile have the wrong birthday? You can easily change it.
When you've opened the QuizUp page (QuizUp tab), located in the middle of the tab bar you should see the Settings icon located in the top left corner.
To change your birthday:
Tap the settings icon in the top left corner
Under settings you'll find the Edit Profile option
There you should be able to edit your birthday
Tap save in the top right corner
Accessing your settings on QuizUp.com is easy - make sure that you are logged in and click the triangle besides your display name on the top bar and select Settings.