The origins of 4/20 as a marijuana holiday have been a mystery for decades. Determining the holiday's origins would end a cultural debate, and untangle the names of those wrongly involved in the origin story of this moniker. This position has been passed on by word-of-mouth, so there is no clear date as to when it began.
The idea that Hitler’s birthday (4/20) has a connection to 4/20, the marijuana holiday, is a theory that holds major acceptance among the public. The theory is well-known and credible enough to have been listed in articles by Time and Newsweek Magazines about 4/20.   Although not the majority opinion, the idea that Hitler and 4/20 are be connected relies solely on the fact that the two events share a date. There is scant information in the historical narrative about the use of 4/20 as a day to celebrate smoking marijuana and Hitler, but that does not mean it is not true. Because the theories share this date, it is likely that 4/20's significance as the marijuana holiday relates to Hitler's birthday.
This argument relies on attributing causation to a vicissitude, or event that has occurred by chance. The correlation of the dates of Hitler’s birth and the infamous marijuana holiday are coincidental rather than causative in origin. There is no evidence that 4/20 originated from Hitler’s birthday, meaning that we see no evidence that anyone selected 4/20 as a marijuana holiday because that day is Hitler’s birthday. The two dates merely overlap. 
[P1] Hitler's birthday, April 20th, led to 4/20 becoming a marijuana holiday.
Rejecting the premises
[Rejecting P1] Hitler has no connection to marijuana or marijuana smokers.