I could easily deny being at a party like that in high school for the simple reason that the first time I was at a party where other teens drank was my Senior Graduation Kegger. It is not that I did not go to parties, it is that I did not go to parties where alcohol was served. I am just a little older than Kavanaugh, and that was actually pretty common back then (no alcohol) unless you hung out with the football team or the stoners, and I hung out with neither. I would not need to know the specific date of a party to be able to offer a blanket denial that I was at a party where there was alcohol prior to a specific month and year.
Yeah, this is all easy for me. I never was invited to a party, never went to a party. I had my first alcohol in college, by myself, just to see what getting drunk was like.