3. Commonly accepted origin
* Snopes.com, High Times magazine, The Marijuana-Logues, and The Straight Dope claim that in the early 1970s, a group of teenagers at San Rafael High School in San Rafael, California, used to meet every day after school at 4:20 p.m. to smoke marijuana at the Louis Pasteur statue. One piece of evidence supporting an origin of the term from the time 4:20 is the fact that the number is always said "four twenty". This theory is also the most cited, and the most widely accepted.
http://en.wikipedia.org/wiki/420_%28cannabis_culture%29