| Bicycle Day | |
|---|---|
 Denver Bicycle Day Parade in 2019. A psychedelic enthusiast wears a lab coat honoring Dr. Hofmann. | |
| Type | Secular & Spiritual |
| Celebrations | Consumption oflysergic acid diethylamide (LSD) or other psychedelics, riding a bike, organizing a bicycleparade,microdosing,psychedelic-themed festivities |
| Observances | Honors the anniversary of the first ever intentional acid trip, undergone by Swiss chemistAlbert Hofmann on April 19, 1943, inBasel, Switzerland, and the impact of the psychedelic revolution for science, medicine and human evolution |
| Date | April 19 |
| Next time | 19 April 2026 (2026-04-19) |
| Frequency | Annual |
Bicycle Day is an unofficial celebration on April 19th of thepsychedelic revolution[1] and the firstpsychedelic trip onLSD byAlbert Hofmann in 1943, in tandem with hisbicycle ride home fromSandoz Labs.[2][3] It is commonly celebrated by ingesting psychedelics and riding a bike, sometimes in a parade,[4] and often with psychedelic-themed festivities.[5] The holiday was first named and declared in 1985 by Thomas Roberts, a psychology professor atNorthern Illinois University,[6][7] but has likely been celebrated by psychedelic enthusiasts since the beginning of thepsychedelic era, and celebrated in popular culture since at least 2004.[8]
On April 19, 1943,Albert Hofmann ingested 0.25 milligrams (250 micrograms) of LSD (Albert Hofmann states in his autobiography[9] that his first experience of the effects of LSD was on Friday, 16th April 1943. (His experience on the 19th April was his first self-administered test of LSD.) Between one and two hours later, Hofmann experienced slow and gradual changes in his perception. He asked his laboratory assistant to escort him home. Due to wartime restrictions on automobile use, they made the journey bybicycle. On the way, Hofmann became anxious as objects in his field of vision wavered and distorted as if seen in a convex mirror. Upon arriving home, Hofmann's condition rapidly deteriorated as he struggled with feelings of anxiety, alternating in his beliefs that the next-door neighbour was a malevolent witch, that he was going insane, and that the LSD had poisoned him. When the house doctor arrived, however, he could detect no physical abnormalities, save for a pair of widely dilated pupils. Hofmann was reassured, and soon his terror began to give way to a sense of good fortune and enjoyment, as he later wrote:
... Little by little I could begin to enjoy the unprecedented colors and plays of shapes that persisted behind my closed eyes. Kaleidoscopic, fantastic images surged in on me, alternating, variegated, opening and then closing themselves in circles and spirals, exploding in colored fountains, rearranging and hybridizing themselves in constant flux ...
The events of this first LSD trip, now known as "Bicycle Day" in memory of Hofmann's bicycle ride home, proved to Hofmann that he had indeed made a significant discovery: apsychoactive substance with extraordinary potency, capable of causing significant shifts of consciousness in incredibly low doses. (The termtrip was first coined by US Army scientists during the 1950s when they were experimenting with LSD.)[10] Hofmann foresaw the drug as a powerful psychiatric tool; because of its intense and introspective nature, he could not imagine anyone using it recreationally.[11] Bicycle Day is increasingly observed in psychedelic communities as a day to celebrate the discovery of LSD.[12][13]
The celebration of Bicycle Day originated inDeKalb, Illinois, in 1985, when Thomas B. Roberts, then a professor atNorthern Illinois University, coined the name "Bicycle Day"[a] when he hosted the first celebration at his home.[14] Several years later, he sent an announcement made by one of his students to friends and online lists, thus propagating the idea and the celebration. His intent at the time was to commemorate Hofmann's original, accidental exposure on April 16, but that date fell midweek and was not a good time for the party, so he chose the 19th to honor Hofmann's first intentional exposure.[14][15][16]