I had to look up “420” to see what it was all about, since presumably they were not celebrating Hitler’s birthday (April 20).
And - guess what - none of the sites could decide why this became “national weed day.” Would you expect otherwise of a bunch of stoners?
“420” was a police code associated with marijuana.
Thus “420” became slang for marijuana and it’s easy to see how April 20 became weed day.
Doesn’t 420 come from 4:20 pm smoke up time?