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

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

"Stu was born on a leap year and in 2024 he has an actual birthday, so this will be his 12th birthday," said Miss Chetwyn.

From BBC • Feb. 26, 2024

But even this system was flawed, because the quarter of a day that leap year adds annually is a bit longer than the solar year’s leftover 0.242 day.

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

“The twenty-ninth of February. She wanted to get married on the leap year because she knew no other woman in her right mind would want to do it.”

From "Native Speaker" by Chang-rae Lee