Retro or Not?

So I was checking my friends blogs as I do every morning over coffee when I ran into a blog I have never read before on dmjuice.com. I was nearly astounded at my findings. The author of this blog is obviously younger than I am, but not that much younger as I am only 30 and she claims that she is working and out of school. The title was something about learning a life lesson about being old (and she is clearly somewhere in her early twenties). So the blog was about how she and her roommate threw a 90's party...has anyone heard of this phenomenon? I sincerely thought it was a typo as I can't think of anyone who has ever had one, I mean 80's parties have been the staple through the 80's and every year since...and here in Germany the teens are going through the 80's phase right now with punk rock type fashion with mullets and rat tail hairstyles. Now we are having 90's parties? She said the best part were the outfits and the music. Hmmm. That is usually the best part about 80's parties...so my question, are the 80's for only those over 30 (or somewhere near this age) to celebrate? Are the 90's the new 80's? If so, I object! I mean the 90's weren't nearly as awful (awesome) for fashion and music as the 80's. She pictures one of her roommate's dresses as a cute geometric sundress...geometric was very "in" last year...and clearly hasn't been since the 80's as I remember the 90's very well (high school and college) and never remember anything geometric. I think this poor girl and her friends are confused. And FYI, if anyone invites me to a 90's party, it better be 2020 or later and the invite better come with a strong definition as to what a 90's party is...because now I am confused!
Auf Wiedersehen.