Celebrated every year on October 6
Mad Hatter Day was created in 1986 by a group of computer technicians in Colorado as a holiday to celebrate sillyness.
The date of October 6 was chosen because of the label that the Mad hatter in Alice In Wonderland has on it’s hat which reads “In this style 10/6”.
The “10/6” actually means “10 shillings and a six pence”. But it can also be read to mean “October 6” especially when you have been staring at numbers for way too long.
The Mad Hatter in the story of Alice in Wonderland was not a far fetched character design.
In the old times when hats were made by hand, hatters often used chemicals to shape the hats which contained unhealthy amounts of mercury.
Being exposed to mercury for a long time causes brain damage.
Therefore hatters often actually went mad.