How did 'International Weed Day' start?

Today is the 20th of April symbolised in weed culture as 420, 4/20, or 4:20.

Marijuana enthusiasts regard this day to be 'weed day', the international day of cannabis. Lovers of pot extra-indulge in the burning of the sacred herb.

This day is the celebration of weed and as more countries legalise it, even those who do not smoke know what it is about. The thick white clouds of weed seem to be slithering its way into the lives of everyday people. As someone recently said "weed is the new nicotine", the new mainstream addiction.

With its surging popularity, the origins of 4/20 still remains a mystery. The numbers do not signify a date although people have interpreted it this way.

One of the popular theories is that 420 is the police code of smoking marijuana in California. This theory doesn't hold water because no such police code exists.

Another theory which seems to the most plausible is that 420 originated from a group of friends known as The Waldos in 1971. The group of friends, Steve, Dave and Patrick.

The pot-loving friends back in '71 heard about a plot of marijuana that belonged to a Coast Guard service member who could no longer take care of it.

The Waldos went treasure hunting in search of this plot of pot. They would meet outside school at 4:20 pm to start their treasure quest. "We would remind each other in the hallways we were supposed to meet up at 4:20. It originally started out 4:20-Louis and we eventually dropped the Louis" Steve told Huffington Post in 2013.

The Waldos never found the plot but 4:20 soon became their code for smoking weed. How did code move beyond California to other parts of the world?

This remains the mystery of 4:20. The origins of the famous number are as hazy as the herb itself.