In Pennsylvania, it is illegal for an adult (someone 18 or older) to have sex with a minor (someone younger than 16), even if the sex is consensual. Those who break the law have committed statutory rape.

Is it weird for a 16 and 18 year old to date?

Is it okay for a 16 yo to DATE an 18 yo? Yes it is perfectly legal to date. Nothing in the question infered sex. People need to get it through their heads that just because you went to a movie together or had dinner together it doesnt entitle anything sexual.