The date is known to social media and movie fans around the world as "Mean Girls Day."
Here's the backstory: In the popular 2004 film that inspired the day, there's a scene where Aaron Samuels (played by Jonathan Bennett) turns to Cady Heron (Lindsay Lohan) in class and asks her what day it is.
"It's October 3," she answers.
CLICK HERE, CNN.com actually has a list of ways to celebrate.
Eat cheese fries or Taco Bell
Because they're delicious but also have meaning to fans.
Who can forget the character Regina George's classic line, "Whatever, I'm getting cheese fries"?
Or her assertion that she couldn't eat Taco Bell as she was on an "all-carb diet."
Try and make 'fetch' happen
Speaking of Regina George, she was so right when she said fetch isn't going to happen. But you can still try and give the slang word some love by using it.
The actress told CNN ina 2016 Facebook Liveinterview that she's "been trying so hard to do a 'Mean Girls 2.' It is not in my hands."
"I know Tina Fey and Lorne Michaels and all of Paramount are very busy," Lohan said. "But I will keep forcing it and pushing it on them until we do it."
Wear pink
Because true fans of the film know that on Wednesdays we wear pink.
Watch the movie
Like, duh.