The first time I heard “420” was in 1982 iirc; 4:20 was the time of day we held the “Safety Meeting”! 
Today, for me, it has many meanings, but is and will always be, THE NUMBER!
p.s.: I’m trademarking “THE NUMBER” here as a new cultivar/strain name. First mention, lol. Hopefully the Simpson’s or South Park didn’t do it. Go Tegrity Farms. 
#420somewhere