Follow these steps to change the date of birth on your account.
1. Sign in your account to ” https://account.live.com/summarypage.aspx ” to change date of birth on my Microsoft Account.
2. Click Change birth date.
3. Click I want to add my correct birth date.
4. You will be redirected to your Account overview page. On your Birth date, click Add.
5. Now, Change date of birth on my Microsoft Account to the correct one, then click Save.