It is 4:19 pm on the east coast of the United States. Without warning, the clock strikes 4:20 pm. Twitter updates erupt from the vast nothingness of the Internet. A Bob Marley song is at least somewhat audible at any one location. Riots break out in the street. There no longer exists law and order, but only anarchy and pandemonium. By 4:21 pm, the US government is overthrown.
Not that this has anything to do with the original point, but how does a clock strike 4:20 without warning?