how to know exact account creation date

that would be the date minus the time you have spend since first creating the account

Its part of the data used to verify that an account is yours if you lose the password etc.


So its obviously not publicly displayed, it'd be like listing your email address and security question/answer on your profile.

If you can't remember it - support also accepts other bits of information, like email address, ZP receipts, security answer, current email and so on.