Somehow the date 4/20 has become associated with marijuana culture. I happen to be old enough to know how this happened.
Back when high schools in California had ash trays in the desks for smokers (yes for reals) and HS got out at 4:15 (1615) they would meet at 4:20 to pass a joint around before catching the bus home. The code for this became 4-20 as in “4-20?” “Yeah dude, 4-20.”
So now we celebrate World Marijuana Day April 20th every year because some kids in CA wanted a toke to take the edge off after school got out.
PSA, it’s a freebie, Opus the Unkillable