leap year

American  

noun

1. (in the Gregorian calendar) a year that contains 366 days, with February 29 as an additional day: occurring in years whose last two digits are evenly divisible by four, except for centenary years not divisible by 400.

2. a year containing an extra day or extra month in any calendar.

---

leap year British  

noun

1. a calendar year of 366 days, February 29 ( leap day ) being the additional day, that occurs every four years (those whose number is divisible by four) except for century years whose number is not divisible by 400. It offsets the difference between the length of the solar year (365.2422 days) and the calendar year of 365 days

---

Etymology

Origin of leap year

1350–1400; Middle English lepe yere

Example Sentences

She was born on 29 February, an elusive day that appears once every four years in a leap year - so she's only had seven birthdays on her actual day in her lifetime.

From BBC • Feb. 28, 2024

The extra accrued time results in Feb. 29 appearing on the calendar every fourth year — leap year — to help the seasons line up.

From Los Angeles Times • Feb. 28, 2024

For centuries, attempts to sync calendars with the length of the natural year have sowed chaos—until the concept of leap year provided a way to make up for lost time.

From National Geographic • Feb. 26, 2024

It’s Pope Gregory and his advisers who came up with the really gnarly math on when there should or shouldn’t be a leap year.

From Seattle Times • Feb. 24, 2024

As this method was clumsy, , Euergetes—very possibly at the advice of his new librarian— proposed a simpler four-year cycle with three years consisting of 365 days each, plus a leap year of 366 days.

From "Circumference" by Nicholas Nicastro