April 18th has a bunch of celebrations to consider:
National Animal Crackers Day
International Juggler's Day - also applies to multi tasking office workers
Newspaper Columnists Day
Adult Autism Awareness Day
International Amateur Radio Day
National Stress Awareness Day
National Wear Your Pajamas to Work Day
Pet Owner's Independence Day
Third World Day
Observed Tax Day is today: Deadline has been extended past the traditional April 15th date because Emancipation Day, a holiday observed in the District of Columbia, which falls on April 15th this year.
Patriot's Day (MA, ME) (3rd Monday of the month) Patriot's Day commemorates the Battle of Lexington and Concord on April 19, 1775; which began the American Revolutionary War.
"Midnight Ride of Paul Revere" Day: Paul Revere makes his famous midnight ride from Charlestown to Lexington, MA, shouting and warning the colonists, "the Red Coats are coming!" as the American Revolutionary War begins. (1775)
Boston Marathon
The House That (Babe) Ruth Built, Yankee Stadium officially opened, 1923
The Great San Francisco earthquake hits, killing 700 people. (1906)
Passover (Jewish - begins at sundown)
Christian Feast Day: Corebus, Galdino della Sala, Eleutherius and Antia, Perfectus, Molaise of Leighlin
St. Aya's Day
Constitution Day, Canada
Independence Day (Zimbabwe) from United Kingdom in 1980
Army Day (Iran)
Invention Day (Japan) 1885
(Photo credits: boxes, homebakedmemories.com; An example of an amateur radio station with four transceivers, amplifiers, and a computer for logging and for digital modes. On the wall are examples of various awards, certificates, and a reception report card (QSL card) from a foreign amateur station; tax day cartoon, amydeardon.blogspot.com; Paul Revere’s Ride, cardcow.com; The elite men runners climb a hill and round a curve near the 1 mile marker of the 112th Boston Marathon in Hopkinton, Mass., on Monday, April 21, 2008, blog.syracuse.com; Great SF earthquake photo by Arnold Genthe shows Sacramento Street and approaching fire, from Steinbrugge Collection of the UC Berkeley Earthquake Engineering Research Center, earthquake.usgs.gov; This ancient wall painting (c. 1994-1781 B.C) appears to depict jugglers. It was found in the 15th tomb of the Karyssa I area, Egypt. The prince is looking on to things he enjoyed in life that he wishes to take to the next world. The fact that jugglers are represented in a tomb suggests religious significance: "round things were used to represent large solar objects, birth, and death", Wikipedia)