This post has been corrected. See the note below for details.

People across Southern California will celebrate what they consider an important holiday Friday by getting comfortable on a couch or finding a nice forest before entering a state of deep relaxation.

That might explain why the underground holiday known as "420," aimed at celebrating the virtues of marijuana ingestion in all its forms, is not attracting any special attention from Los Angeles law enforcement: Most "Weed Day" celebrants plan to be very, very mellow.

Authorities from the Los Angeles Police Department and the Los Angeles County Sheriff's Department said they aren't planning any special measures to seek out those getting high. Spokespeople for the departments said they were not personally aware of the significance of April 20.

"We're not doing anything special," LAPD Officer Rosario Herriera said. "We always have a sufficient amount of officers out on a daily basis."

The origins of celebrating marijuana on April 20 are hazy. Observers speculate that it started with the numbers of local penal codes related to marijuana possession or to a random date selected by weed enthusiasts.

The Wall Street Journal reports that there were 17.4 million marijuana users in 2010, up from 14.4 million in 2007, all signs that the underground pot holiday may be gaining more steam.

Some Southland residents will be celebrating 420 with music and discounted cannabis.

Outside of Coachella, the music festival where many have indulged themselves without the holiday, Festival 420 is set to hit the San Bernardino County Fairgrounds on Saturday with a musical slate chock full of bands and DJs. The festival explicitly states that no illegal drug use or possession is allowed.

A 420 Hangover Festival is also scheduled to be held at the Observatory in Santa Ana, though a day after the big holiday.

And according to local cannabis websites, some retailers are offering discounted product on Friday. Kushmart in Hollywood, for example, is advertising a "Huge 420 sale," with 50% discounts and more.

[For the Record, April 20, 12:46 p.m.: A previous version of this post stated that local law enforcement spokespeople were personally aware of 420. They said they were not.]

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-- Matt Stevens

twitter.com/mattstevenslat

Photo: Musical artist Snoop Dogg celebrates "420" a few days early at the Coachella Valley Music and Arts Festival. Credit: Luis Sinco / Los Angeles Times