When the clock ticks 4:20 p.m. on April 20 a number of students plan to light up for the unofficial 420 event celebrating marijuana use.Last year, hundreds of students gathered on the Redstone Green April 20 until police presence broke up the crowd at about 4:26 p.m., the Cynic reported.But when did this event first begin?Despite rumors that 420 was a police code for marijuana smoking in progress or that it comes from the number of chemicals in marijuana, the term was first coined by a group of California high school students, according to the Huffington Post.In 1971, five students called the Waldos ? because their chosen hangout spot was a wall along the school ? would smoke everyday after sports practice at 4:20 p.m. and drive down to Pt. Reyes peninsula in search of a hidden treasure of marijuana plants, the article stated.The idea of celebrating the illegal substance on April 20 gained popularity throughout the 1970s, according to the Huffington Post.Students at UVM began an annual campus smoke-in throughout the mid-1990sas a way to protest marijuana laws, according to the Associated Press.The event grew over the years until officials intervened in 2001 and 2002.