How Do I Find Out The Date I Actually Created My Yahoo E-mail Account?

When you created your Yahoo E-mail Account, you should receive automatic mail from Yahoo with 'Welcome to Yahoo!' as the subject. Just see the date and that was when your email account created. Even you can know the hour and minute too =D

It depends on the provider,
But usually you will get 'welcoming mail' when you were registered so you can look the email date.

Some provider mention your join date at your profile, you can check it too.

It is in the profile page, you can check every person there

Well the date should be somewhere on your account page or homepage.If it isn't you could try emailing Yahoo and asking them directly.