What is 420's derivation?

According to Wikipedia and Urban dictionary, 420 is not a police code. It came from a group of 1971 high schoolers that loved the reefer. They established a meeting time of 4:20 to smoke marijuana - allowing themselves enough time to complete their sports practices and get to the Louis Pasteur statue that they assembled at. Somehow, the term travelled all the way to the 21st century.