I would start my own thread on this, except that I am interested in the exact same thing as the OP. The original poster wrote:
Is there a way that once I go in to someone´s profile I can see his/her age but not his birthday?
This is currently not possible with the settings unfortunately.
You can display just a birthday or a birthday with one's age. But you cannot display just your age without your birthday. I don't mind showing my age, but I am a bit pickier about showing my birthday to non friends for security reasons (doctors office and such always ask for this info to verify that I am who I claim to be). Should I create a voice page for hiding your birthday? Having this option would enable us to display just your age.