Adams's prediction was off by two days. From the outset, Americans celebrated independence on July 4, the date shown on the much-publicized Declaration of Independence, rather than on July 2, the date the resolution of independence was approved in a closed session of Congress.
LSD effects usually last for 12 hours. But LSD can stay in your system for up to 5 days after use. More on the bioavailability, half life and detection window
It's not known exactly how LSD affects the brain. Scientists believe it has to do with serotonin. Serotonin is a brain chemical that carries messages related to perception and behavior. LSD somehow disrupts that process, leading to a trip that can last for 12 hours or more. A person starts feeling high about 30 to 90 minutes after taking LSD. How the drug actually affects a person depends on many things, including the amount of LSD taken, the person's surroundings, and his or her personality and mood.