You cannot change your age directly in Discord settings
If your birthdate is incorrect, submit an age update request to Discord Support
Go to the Discord Support website
Choose the option for updating age or date of birth
Enter your email address
Enter your Discord username
Provide the correct date of birth
Upload a clear photo of a valid ID showing your date of birth
If requested, include a photo of yourself holding the ID and a note with your Discord username and current date
Submit the form
Wait for Discord Support to review your request
Check your email for updates from Discord Support