To change your account birthdate, you must log in to Texyon and go to your profile.
In the upper right you will find the Settings button, where you will see the Change birthdate option.
When you have requested a birthdate change, an email will be sent to your inbox with a link.
This link will redirect you to a new page which will ask for your password and the new birthdate.
Check your Spam folder in case you don't receive the message with the link. If you don't receive it, send a ticket from the account where you are trying to change the data.