If you are anyone older than 13 you know what 420 means and what 420 day means. Its the celebration of weed in America and most people light up to celebrate as some don't go to work or leave early to smoke.

The reason why 4/20 or April 20th was chosen was because the most credible story traces the date to Marin County, Calif. In 1971, five students at San Rafael High School would meet at 4:20 p.m. by the campus’s statue and partake in the activity. The students would use 420 as code not only for the time they would meet but cause it was code for weed. The story of group spread to tons of rock bands in the 70s and 80s and eventually made it worldwide. The group was eventually recognized with this in the 1990s with the new publication "High Times"

So be careful out there and know the Michigan rules of marijuana so you aren't arrested.