Bicyicle day, the day that Albert Hoffman, the first synthesizer of LSD and had the first recorded trip ever, The term comes from Hoffman going on a bike ride back to his home from a lab in Basel, Switzerland after ingesting 250 ug of the substance (250 micrograms). He would go on to describe the way he felt while tripping balls
Donât do too much acid on 4/19 or you will get hppd (hallucinogenic perception disorder)