Modifying the demographic form

The official calendar of Nepal is Bikram sambat (BS). People’s birthdays are registered in BS. I have a conversion function from BS to English date (AD). I would like to add one more field, DOB (BS), in the demographic and patient portal form such that it will populate the data into DOB (AD). My question is where I can modify the code in the demographic and patient portal registration form?. Much appreciated for any helps.

You can modify (add or delete) demographics fields, In Admin/Forms/Layouts choice demographics.
You can watch this video for modification or new form.

Hi Hari Khanal,
1.Change any field in demographics modify admin->forms->layouts
2.modify any field in patient portal registration form you can modify in portal/account/register.php file

you can refer below attached link to know about OpenEMR Patient portal registration form