April 15

Calendar and numbering

The day’s position within the year follows the conventions of the Gregorian calendar. Because of the leap-day adjustment every four years, dates after February shift their ordinal number by one in leap years. Many annual observances follow fixed calendar dates like April 15 rather than a weekday-based schedule.

Notable historical events

• April 15, 1912 — the RMS Titanic sank in the North Atlantic after striking an iceberg, a defining maritime disaster of the early 20th century.
• April 15, 1865 — U.S. President Abraham Lincoln died after being shot the previous evening; his death had profound political and social consequences for post–Civil War America.
• April 15, 1947 — Jackie Robinson made his major league debut for the Brooklyn Dodgers, a milestone in the integration of professional baseball in the United States.
• April 15 is also the birthday of some well-known historical figures, most notably Leonardo da Vinci (born April 15, 1452), and the date is used by cultural organizations to celebrate visual arts.

Modern observances and uses

Several contemporary observances and customs fall on or around April 15. In the United States the federal individual income tax return deadline is customarily April 15, though that due date may be moved when it falls on a weekend or public holiday. Major League Baseball recognizes April 15 as Jackie Robinson Day, when players across the league honor Robinson by wearing his number 42.

Distinctions and notable facts

Dates like April 15 illustrate how a single calendar day can link disparate themes—disaster and remembrance, legal and fiscal deadlines, and cultural commemorations. Because the date is fixed, it often serves as a convenient anchor for annual rituals, news anniversaries and educational programming.