February 29, also known as the leap day of the Gregorian calendar, is a date that occurs in most years that are divisible by four, such as 2012, 2016, 2020, and 2024. Years divisible by 100, but not by 400, do not contain a leap day — 1700, 1800, and 1900 did not contain a leap day.
Years containing a leap day are called leap years.
On Leap Day, 1796, the Jay Treaty between the United States and Great Britain went into force, facilitating ten years of peaceful trade between the two nations.
A “leapling” is a person born on a leap day. Famous leaplings include Italian composer Gioachino Rossini (1792), American poet Howard Nemerov (1920), American fantasy author Tim Powers (1952), and Ukrainian-American lawyer and educator Eugene Volokh (1968).