To update your profile:
login to http://yahoo.com
Go to http://manage.members.yahoo.com/index_listprofiles.html
Near the top of the main box, you'll see one or more rows about "Yahoo! ID:"
Click on the Edit button near the middle of the relevant profile.
On the resulting page, a few lines down in the center, ...
click on "Edit Profile Information".
Enter a number in the "Age:" field (fourth).
scroll to the bottom, click on "Save Changes".

To update your profile:
login to http://tribe.net
click on "update my profile" (left, in black)
click on "edit bio" (probably on left, in black)
under "Basic Information", fourth line: "birthday"
- uncheck "Don't show my age" on the right.
- scroll to bottom right, click red "save".