April 18 is the 108th day of the year (109th in leap years) in the Gregorian calendar.[1] The date holds historical significance for initiating key conflicts and disasters, including Paul Revere's midnight ride on April 18, 1775, which warned American colonial forces of advancing British troops and precipitated the Battles of Lexington and Concord, the first armed engagements of the American Revolutionary War.[2] On April 18, 1906, a magnitude 7.9 earthquake struck San Francisco, rupturing 296 miles of the San Andreas Fault, destroying much of the city through shaking and subsequent fires that burned for three days.[3] During World War II, the Doolittle Raid occurred on April 18, 1942, when sixteen U.S. Army Air Forces B-25 bombers launched from the USS Hornet struck targets in Japan, marking the first American air attack on the Japanese homeland and boosting Allied morale despite limited physical damage.