Customers don't like to be asked their date of birth during the account creation process but TB does not provide an easy way to hide this request.
Thankfully it can easily be hidden with a little custom CSS.
The following lines need to be added to the "Add extra css to your pages" section in the "Preferences/Custom Code" area of your TB back office:
/* For desktop browser account creation, add this line: */
.account_creation .date-select { display: none; }
/* For mobile browser account creation add this line: */
#opc_account_form .date-select { display: none; }
/* For the user's "My account" page that they can see after they sign up, add this line: */
#identity .std .date-select { display: none; }
The commented lines (/* ... */) do not need to be added, only the CSS lines that start with . or #. Copy & paste to avoid errors.
I have tested the above on TB 1.0.8 with the standard community theme (obviously) and it is working without trouble. It may work with other themes as well but test before deploying.
Thanks to @Brent Dacus for suggesting to put this CSS in the Custom Code area instead of modifying the template's global.css file directly.