This year has been a big one for pop culture anniversaries. Friends turned 10 making Ross's son, Ben, almost 20 now. Some of our favorite albums from the '90s  turned 15 this year — including Britney Spears 's . . . Baby One More Time and Christina  Aguilera's divalicious debut — and many killer teen movies  did too. While exciting, it's not all sweet nostalgic feelings — it forces us to look at just how long it's been since those good old days. Keep reading to see 25 mind-blowing pop culture facts that will make you feel ancient, from the demise of YM magazine and other 2000s trends  to exactly how long ago Mary-Kate and Ashley  Olsen made a splash in matching outfits.
Source: NBC 
It Takes Two came out 19 years ago.
Mary-Kate and Ashley's matching style has changed a lot in two decades.
Source: Getty / Barry King, Taylor Hill 
Remember Nicky and Alex from Full House?
This is them now. They're 23.
Dylan Tuomy-Wilhoit (Alex) is on the left, and Blake Tuomy-Wilhoit (Nicky) is on the right.
Source: Twitter user DC_Wilhoit 
Friends started two decades ago.
Friends premiered in 1994 and ended on May 6, 2004.
Ross's son, Ben, from Friends would be 19 now.
As for the rest of the kids? Monica and Chandler's twins are 9, Emma is 11, and Phoebe's triplets are turning 16 this year.
Sex and the City has been off the air for 10 years.
Christina Aguilera's debut album turns 15 this year.
"Genie in a Bottle" wasn't the only hit song from 1999, though — see 14 other albums that came out 15 years ago .
This is how Miley Cyrus used to dance, back when she was Hannah Montana.
And this is what Miley considers dancing now.
Source: RCA Records 
Nipplegate happened a decade ago.
Relive every moment of Janet Jackson and Justin Timberlake's Super Bowl scandal  here.
Grey's Anatomy is in its 11th season.
Denny Duquette died eight years ago — RIP.
And George O'Malley died six years ago.
Titanic hit screens 16 years ago.
To get even more nostalgic, read all the sweet things Leonardo DiCaprio  and Kate Winslet  have said about their friendship  through the years.
Source: Getty / Kevin Mazur, Mike Marsland 
Clarissa Explains It All started 23 years ago.
This GIF explains how we feel about it.
Source: Nickelodeon 
And 18 years ago, we first met Sabrina the Teenage Witch. We miss you, Salem.
The first Harry Potter movie came out 13 years ago.
This is the cast at their first premiere in 2001 and their last in 2011.
Source: Getty / Evan Agostini, Stephen Lovekin 
Cruel Intentions turns 15 this year.
Reese Witherspoon , Ryan Phillippe , and Sarah Michelle Gellar  all have kids — Reese and Ryan have two together — and a bunch of other great '90s movies turn 15 this year  too.
Britney Spears's kids are 8 and 9 years old.
Jayden James is 8, and Sean Preston is 9.
The year that Marty McFly flies to in Back to the Future 2 is 2015.
It's only about a year away. Gulp.
The kids from the cartoon Recess would all be 26 now.
SpongeBob SquarePants has been on for 15 years.
Source: Nickelodeon 
And lastly, YM hasn't been on newsstands for a decade.
Pour one out for the young and modern, plus other amazing lost 2000s trends .
Source: YM Magazine