What is the significance of the number 420 in relation to marijuana?

I always heard that it is some kind of police code, for some kind of marijuana offense. But apparently that isn't true at all. According to snopes.com, it originated in 1971 at San Rafael High School in California. It was just a slang term that some kids used to remember when they were all supposed to meet up to smoke weed (at 4:20 pm). It caught on from there.

See the Related Link below for the snopes.com entry.