"In the early 1970s a small group of hippie stoners at San Rafael High School in northern California used to meet at a designated location every day at 4:20 p.m. to smoke weed. They did this so regularly that among members of the group — who called themselves "the Waldos" — the expression "420" became a euphemism for "time to light up."
▼ SoCalExile
What's an interesting coincidence is that there are emails that have been FOIA'd from the ATF here: http://www.sdslaw.us/single-post/2016/11/22/ATF-Delivers-Documents-in-NFATCA-FOIA-Case
Read part 2 page 420:
http://i.imgur.com/WiixxHv.png
Odd Pizza reference there.
▼ TheGettysburgAddress
420 = San Rafael High School = Marian County CA = Zodiac
http://urbanlegends.about.com/b/2011/04/19/420-meaning.htm
"In the early 1970s a small group of hippie stoners at San Rafael High School in northern California used to meet at a designated location every day at 4:20 p.m. to smoke weed. They did this so regularly that among members of the group — who called themselves "the Waldos" — the expression "420" became a euphemism for "time to light up."
▼ Eyeonit
4:20 = Time to smoke some weed.
▼ gooppoop
Also could just mean he's about to smoke up.