How is Difference in Age Measured

My question involves criminal law for the state of: PA

In a case where age difference is important such as statutory rape, how is the difference measured?

Example: a male with the birthdate 4/25/1995 (18 years of age) and a female with a birthdate of 5/15/1997(15 years of age).

Is the difference in age 2.1 years, or is it 3?

It depends on the statute. The difference can be one of years difference or years old. This forum is for legal issues, it is not the how to screw a minor and get away with it forum. I suggest you consult her parents or the local police for assistance.

The incident already occurred a couple of years ago, only kissing. Nothing else. I've worried myself sick over a possible false accusation of statutory rape, and I'm just trying to diffuse my anxiety. I have no interest in doing what you think I'm trying to do.

Absent clear authority to the contrary, assume that a difference in age will be measured in the manner most likely to land you in prison.