I ran into an issue where a game decided I was only 18, and then wanted to verify that I did put in the right brithdate. I basically found a method to change my birth date for my iTunes account, which should prove helpful for some.
1) In a browser of your choice, go to : appleid.apple.com
2) Select Manage your account, which prompts you to log in.
[zp src=”itunes-manage.jpg” album=”blog/itunes-brithdate/” width=”600″]
3) Once signed in, select “Password and Security” option on the left.
[zp src=”itunes-passwordsecurity.jpg” album=”blog/itunes-brithdate/” width=”600″]
4) Then use the drop downs to change your brith day, month, and year if needed and hit save.
[zp src=”itunes-birthdate.jpg” album=”blog/itunes-brithdate/” width=”600″]
Voila! Hopefully someone finds this useful.