April 19th might just seem like another day for casual bike enthusiasts, but there’s a twist. Instead of merely honoring your average two-wheeled joyrides, Bicycle Day tips its hat to a psychedelic voyage of epic proportions.

Forget what you thought you knew about this pseudo-holiday, because it’s not just about cycling. We’re here to shine a light on the fateful day in 1943 when Albert Hofmann, Swiss chemist and LSD creator, treated himself to a mind-altering bicycle ride. You heard that right—our guy Albert inadvertently discovered the mind-expanding properties of LSD while cycling around Basel, Switzerland.

According to Rolling Stone, Hofmann chose the iconic time of 4:20 p.m. on April 19th to dose himself. What ensued was a trip (pun fully intended) through a kaleidoscope of “fantastic images,” as Hofmann later detailed in his memoir, LSD: My Problem Child. He rode six miles that day, but the experience was more about the journey than the destination.