In case I wasn't the only one to wonder what the hell "420" is, and in case anybody cares, I found this explanation:-
"According to Steven Hager, editor of High Times, the term 420 originated at San Rafael High School, in 1971, among a group of about a dozen pot-smoking kids who called themselves the Waldos, who are now pushing 50. The term was shorthand for the time of day the group would meet, at the campus statue of Louis Pasteur, to smoke pot. Intent on developing their own discreet language, they made 420 code for a time to get high, and its use spread among members of an entire generation.
It's now well known across the world and we all blaze at 4:20pm and on the 20th day of the 4th month "420" it's like a stoner holiday"