Bicycle Day
April 19, 1943 — the first deliberate LSD trip, on a bicycle. Science has always been curious.
About
Bicycle Day on April 19 commemorates one of the most unusual events in the history of chemistry: on this date in 1943, Swiss chemist Albert Hofmann intentionally ingested a small amount of LSD — a compound he had synthesised five years earlier — and cycled home from his laboratory in Basel, experiencing the world's first deliberate LSD trip along the way. Hofmann had accidentally discovered LSD's psychoactive effects three days earlier; the April 19 self-experiment was his attempt to study those effects systematically. His ride home became the namesake event. LSD subsequently became one of the most studied and controversial substances in pharmacological history, associated with both the 1960s counterculture and serious psychiatric research. Today, there is renewed scientific interest in psychedelic-assisted therapy for treatment-resistant depression, PTSD, and anxiety. Bicycle Day is observed by researchers, harm-reduction advocates, and those interested in the intersection of chemistry, consciousness, and medicine.
History
Albert Hofmann first synthesised LSD-25 in 1938 at Sandoz Laboratories, but its psychoactive properties went unnoticed until April 16, 1943 — accidentally. On April 19, he conducted a deliberate experiment, ingesting 250 micrograms and cycling home as effects intensified. His detailed account, published in his 1979 memoir 'LSD: My Problem Child,' remains a foundational document in psychedelic science.
Where It's Observed
Cultural Context
US United States
The US has become the centre of the psychedelic renaissance. Research at Johns Hopkins, NYU, and MAPS is producing clinical evidence for therapeutic LSD and psilocybin use. Bicycle Day is observed by the research community as a moment to reflect on the history and future of psychedelic science.
KR South Korea
Bicycle Day is not widely observed in South Korea, where psychedelic substances remain tightly controlled and culturally stigmatised. However, growing awareness of international clinical research is beginning to open academic conversations about the therapeutic potential of these compounds.
JP Japan
In Japan, LSD is a Class 1 controlled substance, and Bicycle Day is known only in niche scientific and cycling communities. The day is occasionally referenced in popular culture contexts as a curious episode in chemistry history rather than a serious occasion.
How to Participate
- 01Read Albert Hofmann's account of April 19, 1943 in 'LSD: My Problem Child'
- 02Learn about current clinical trials using psychedelic-assisted therapy
- 03Go for a bicycle ride and appreciate the simple act of movement
- 04Explore the history of consciousness research and its intersections with medicine
Frequently asked questions
When is Bicycle Day?+
Bicycle Day is observed annually on April 19. The date is fixed each year — April 19 — and does not shift based on the lunar calendar or weekday.
What is Bicycle Day?+
Bicycle Day on April 19 commemorates one of the most unusual events in the history of chemistry: on this date in 1943, Swiss chemist Albert Hofmann intentionally ingested a small amount of LSD — a compound he had synthesised five years earlier — and cycled home from his laboratory in Basel, experien…
Is Bicycle Day a public holiday?+
Bicycle Day is an international observance or awareness day, not a public holiday in most countries. It does not typically result in days off work or school closures, though some countries and organisations hold official events.
How can I participate in Bicycle Day?+
Read Albert Hofmann's account of April 19, 1943 in 'LSD: My Problem Child' Learn about current clinical trials using psychedelic-assisted therapy Go for a bicycle ride and appreciate the simple act of movement These are some of the most accessible ways to engage with the day's purpose.
Which countries observe Bicycle Day?+
Primarily observed in scientific and harm-reduction communities globally.
Mark the date
Download a free printable calendar for 2027 and never miss Bicycle Day.
US United States
United Kingdom
Australia
Canada
KR South Korea
JP Japan