What is the Database meta key of User registration Form submitted Date..

Hello,
I wanted to print the User registration form Submitted date on E2pdf Pdf for that I needed Metakey of that registration form Submitted date.. so I can fetch the meta value… It’s showing registration form submitted Date on Info pop-up.. saying date of submission.. I need that meta key from Database table.. or please tell me where it is located in Database on which table.. to get registration form submitted Date please help.. ??