Below are two ways you can establish your Gmail account creation date.
Find Gmail Account Creation Date
1. Gmail Welcome Email:
All Gmail accounts receive a “Welcome to Gmail” email after being created. This “welcome email” has the same date as your Gmail account creation date. Go to your Gmail inbox and click the “oldest” button to get the last message. This message will be from the Gmail team. Note this email’s date, and consider forwarding it to any back-up email account that you have. And you’re finished!
But many readers have said that they deleted the welcome email and so are unable to get the account creation date. If you are one of these people, proceed to the second point.
Go to Settings -> Forwarding and POP/IMAP.
Status: POP is enabled for all mail that has arrived since “Your Account Creation Date”and you will get the required date.