April 20 isn't just a holiday for stoners: In a world where recreational marijuana is legal in eight states, it's basically the entire Christmas shopping season rolled into a single day for pot businesses. 

"We're just expecting to get slammed," the owner of a smoking room in Colorado tells CNN. One expert expects to see an increase in business of 30% to 40%, especially as some marijuana retailers are offering discounts of up to 50%.

 It's no wonder Thursday is being called a "really good time to stock up" for potheads. Here's what else you need to know about 4/20:

  • There's a lot of incorrect information floating around about the origin of the term "420." Mental Floss sets us straight, revealing that it started in 1971 with a group of California high-schoolers whose personal slang—referring to the time of day they met up to smoke—caught on with the Grateful Dead.
  • But do we really need 4/20 as a rallying point anymore? That's the question Rolling Stone asks as the legalization of weed goes mainstream. Snoop Dogg, for one, says yes, calling it one of his "favorite days."

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