Is it okay to date at the age of 19?

No. Its not wrong AT ALL. Youre both of legal age to date each other. However, if he holds the age thing over your head or uses it to treat you in any way less equal or pull any other kind of power move, then he has issues you dont want to deal with.

Whats the oldest a 19 year old should date?

This rule states that by dividing your own age by two and then adding seven you can find the socially acceptable minimum age of anyone you want to date. So if youre a 24-year-old, you can feel free to be with anyone who is at least 19 (12 + 7) but not someone who is 18.