Let me change my birthday, please. No one gives you their real birthday at first
Allow users to correct their birthday.
Problem - most people don't give yahoo accurate data until they know they want to use the email as more than a burner account. As a result, incorrect or incomplete data is entered upon account creation.
Solution - as users decide to stick with a yahoo account, allow them to correct their information, especially birthdays.
Benefit to the user - our information is more secure (it's annoying that currently we're not allowed to change our birthdays for "security reasons.") For security reasons, it would be far more secure to allow us to edit all information to be correct.
Benefit to Yahoo - it's far more useful / profitable to have accurate user data.
Thanks.