Factgirl's fact of the day:

This FOTD is for you youngsters:

420 - Code to pot smokers for "time to smoke" or "got spleef?"
4:20 - Ceremonial time of day many pot smokers light up
4/20 - April 20, day when many pro-pot organizations have ceremonies
4-20 - NOT San Rafael California police code for "pot smoking in progress" - in fact there is no 4-20 code at all

The term 420 (for twenny) started at San Rafael High School in the early 1970's by a now legendary group of outcasts called the Waldos. School let out at 3:10, and a few had after school activities that lasted an hour - they met every day by a statue of Louis Pasteur at - you guessed it - 4:20. 420 stayed pretty much within the Deadhead community in the 70's and 80's but spread quickly throughout pot society in the 90's.

A side note: Now that you know this fact you will suddenly become very aware of how many times the number 420 comes up... TV shows, commercials, addresses, even nursery rhymes (HOW many blackbirds baked in a pie..?).

-it's a fact!

sources: April 20 San Francisco Chronicle, High Times Magazine May 97 and Dec 98