is it against the law for a 18 yr old male to date a 15 yr old female if they are not having sex

I am a lawyer in CT and practice in this area of the law.  it is ok for a 15 and 18 year old to be friends.  if these is any sexual contact, you are playing with fire as the legal age to consent is usually 16 years old.  i suggest that you wait on being anything more than friends for another year.

Although I do not practice law in the State of Georgia, here are my initial impressions.  I agree with my colleague's advice that you are "playing with fire."  Illegality will all come down to your definition of the word "date".  Even if you do not have sexual contact, you may expose yourself to criminal liability for a serious of other actions with this girl, including but not limited to giving her alcoholic beverages, watching inappropriate movies, or having sexually suggestive conversations.  I suggest that you terminate your relationship rather than risk going to jail.