People are actually celebrating 90210 Day.
If you're not familiar with this show, it was an ongoing saga focused on rich teenage kids (who were inexplicably played by 28 year olds) and the insane high school and post-high school shenanigans that rich teenage kids are known to get into. It was a less funny Saved by the Bell or, to be more contemporary, a less sexy Gossip Girl. My sister was a loyal fan and from the few episodes I sat through, I recall it to be mostly about people taking high school very, very seriously.
The show -- which spawned spinoffs and a remake that's still on the air -- ran from 1990 to 2000, at which point most of the actors floated off into oblivion.
But that's not stopping fans of the show (or perhaps just fans of '90s nostalgia in general) from gathering for parties today and celebrating on Facebook. It's unknown whether or not these fans will wear some of the ridiculously high-waisted jeans and poofy hair styles made popular by the program.