‘Stoner eclipse’: 420 Day this year is a palindrome that won’t happen again for 1,000 years

4/20 celebrations in San Francisco's Golden Gate Park, Hippie Hill

The high holiday, 4/20, has rolled around, and San Francisco is once again playing host to the largest free cannabis event in the state. The day includes a full roster of events at Golden Gate Park's Hippie Hill, where the city expects about 20,000 people to pack the park.

LOS ANGELES - While most Americans prepare for the upcoming April 8 solar eclipse, marijuana enjoyers will be preparing for the "stoner eclipse" when April 20, commonly known as the unofficial holiday dedicated to celebrating and smoking marijuana, is celebrated as a palindrome this year.

The trippy event won’t happen again for another millennium, with the next 420 palindrome happening on April 20, 3024.

Many weed enthusiasts have already begun celebrating the particular date's rarity. One user on Reddit commented, "It’s the only time it’ll happen in history. Like a stoner eclipse!"

"Palindromic Danksgiving incoming!" wrote another social media user.

What is a palindrome?

A palindrome is a word, phrase, number, or other sequence of characters that reads the same forward and backward. In other words, it remains unchanged when its characters are reversed.

For example, "racecar," "madam," and "level" are all examples of palindromic words.

Palindromes can also be longer phrases or sentences, such as "A man, a plan, a canal, Panama!" or "Was it a car or a cat I saw?" Due to their unique symmetry, palindromes are often used as wordplay or in puzzles.

Palindrome dates in 2024

In total, April will have eleven palindrome dates.

April 2, 2024 (4-2-24)
April 20, 2024 (4-20-24)
April 21, 2024 (4-21-24)
April 22, 2024 (4-22-24)
April 23, 2024 (4-23-24)
April 24, 2024 (4-24-24)
April 25, 2024 (4-25-24)
April 26, 2024 (4-26-24)
April 27, 2024 (4-27-24)
April 28, 2024 (4-28-24)
April 29, 2024 (4-29-24)

What is 420 Day and where did it originate?

The National Day Calendar designates April 20 as 420 Day, an annual celebration where cannabis producers, consumers, and advocates come together to commemorate and enjoy marijuana.

Previously considered unconventional, this day now serves as a unified call for the "Once an unconventional day, the day has become the rallying cry of those who seek to legalize marijuana for medicinal and recreational uses," the National Day Calendar writes on its website.

While federal law in the United States still classifies cannabis as illegal, many states have legalized the substance for medicinal or recreational use — or both.

A man prepares a marijuana cigarette during a 4/20 rally to commemorate the World Cannabis Day in Bogota on April 20, 2022. (Photo by Raul ARBOLEDA / AFP) (Photo by RAUL ARBOLEDA/AFP via Getty Images)

Since the 1970s, numerous myths have circulated globally, especially across social media, regarding the origin of the date 4/20, yet most accounts remain unverifiable. One widely circulated tale suggests that during the 1970s, a group of teenagers from a California high school established the tradition of smoking marijuana at precisely 4:20 each day, adopting "420" as their secret code for the drug.

The five students called themselves the "Waldos," which referenced the wall they would sit on at their school. The origin of the Waldos has been documented in letters, military records and high school newspaper clippings to corroborate these origins.

Stephanie Weaver contributed to this story.