Bicycle Day

Bicycle Day History

Bicycle Day seeks to commemorate the day Swiss chemist Albert Hofmann purposefully ingested LSD-25, or Lysergic Acid Diethylamide. In his research to create an anti-hemorrhaging drug using ergot fungus, Hofmann had accidentally been exposed to the synthetic chemical LSD. Noticing some adverse effects such as dizziness and restlessness, Hofmann decided to ingest what he believed to be a safe dose, .25 milligrams, a few days later.

Bicycle day recognizes Hofmann’s experience with LSD in 1943 and acknowledges it as the first acid trip. After ingestion, Hofmann became anxious and paranoid and asked his assistant to accompany him home. Together they biked to Hofmann’s home, hence the name of the day. After seeing a doctor and finding nothing wrong physically, Hofmann calmed down. He would later describe his experience, kaleidoscopic, fantastic images surged in on me, alternating, variegated, opening and then closing themselves in circles and spirals, exploding in color fountains… It was particularly remarkable how every acoustic perception became transformed into optical perceptions. Bicycle Day was created in 1985 by Northern Illinois University professor Thomas B. Roberts. He started the day as a celebration of the first intentional exposure to LSD. It is observed annually on April 19th.

Top 8 Facts for Bicycle Day in 2026

• Swiss chemist Albert Hofmann recorded in his laboratory notes that he performed his first intentional self-experiment with LSD-25 at precisely 4:20 p.m. on April 19, 1943.
• While Hofmann intended to take a cautious "threshold dose" of 250 micrograms, this amount was actually more than ten times the dose needed to produce psychoactive effects, leading to a much more intense experience than he anticipated.
• The iconic bicycle ride occurred because motor vehicle use was restricted in Switzerland due to World War II fuel shortages, forcing Hofmann to be escorted home by his laboratory assistant, Susi Ramstein, on a pedal bike.
• During the journey, Hofmann experienced terrifying hallucinations where he believed his neighbor was a malevolent witch and feared he had become possessed by a demon, though he later described the experience shifting into a state of "unprecedented colors and plays of shapes" once he was safely in bed.
• The observance was not established until 1985, when Northern Illinois University professor Thomas B. Roberts coined the name Bicycle Day to commemorate the event, choosing the 19th over the 16th—the date of Hofmann’s first accidental exposure—simply because it fell on a better day for a celebration that year.
• Albert Hofmann’s lifelong, complex relationship with the substance he discovered is famously documented in his memoir, LSD: My Problem Child, where he advocated for its use as a psychiatric tool rather than a recreational drug.
• The unofficial psychedelic holiday is frequently confused with the United Nations-recognized World Bicycle Day, which is observed on June 3 to promote the health and environmental benefits of cycling.
• Modern celebrations of the day often feature intricate "blotter art" and tributes from visionary artists such as Alex Grey and Android Jones, who create works reflecting the kaleidoscopic visuals reported by Hofmann during his original trip.

In the News and Trending in the US for Bicycle Day

Top things to do in the US for Bicycle Day

• Explore the virtual Albert Hofmann museum.
• Learn more about psychedelics using an academic psychedelic bibliography.
• Watch a movie that poses a question, asks why, or challenges normal frameworks. Here are our suggestions:
  Cloud Atlas (2012)
  Enter the Void (2009)
  Waking Life (2001)