No, we dont save time of kills, it's just a waste of space if we do so..
Locked, it's not possible to get registration date of players registered before the account update..
Off-topic:
You are advised to register a primary account. Once it's approved, you can create normal accounts without admin approval, add all your existed account into your account list and play using any of the account in your account list without the need to login to each one of them, as long as you're logged into your primary account. Primary account is like a master key in which you can access all the account in your account list. So, you dont have to remember all your accounts nick and their password after adding them to the account list, you can check the last IP logged into your accounts in the list to find any sign of account break and you can still access your normal account even though it was broken by someone and pass got changed, as long as you can access your primary account and the account is still in the list. But make sure you dont use same password as in other server/website and disable auto-login for the account if you share PC.