leap year

From Late Middle English lepe-yer, lep-yer (“year with 366 days, leap year”),^[1] from lep, lepe (“act of jumping, jump, leap”)^[2] (from Old English hlīep, hlȳp, probably ultimately from Proto-Indo-European *klewp- (“to spring; to stumble”)) + yer (“calendrical unit based on a complete revolution of the Earth around the Sun, year”) (from Old English ġēar, ultimately from Proto-Indo-European *yóh₁r̥ (“year”)). The English term is analysable as leap (noun) +‎ year, and possibly relates to the phenomenon that any fixed date of a 365-day calendar advances one weekday each year but every date of a 366-day year after February 29 (often seen as the leap day) advances by two weekdays instead.^[3] For example, Christmas (December 25) fell on a Saturday in 2004, a Sunday in 2005, a Monday in 2006, and a Tuesday in 2007 but then “leapt” over Wednesday to fall on a Thursday in 2008 which was a leap year.

Compare also Old English mōnan hlȳp (“moon’s leap”) and Medieval Latin saltus lūnae (literally “leap moon”), an additional day added every 19 years (a Metonic cycle) to bring the lunar and solar calendars into alignment.^[3]

• (Received Pronunciation) IPA^(key): /ˈliːp ˌjɪə/
• (General American) IPA^(key): /ˈlip ˌjɪ(ə)ɹ/

• Audio (General American):

  (file)

leap year (plural leap years)

1. A year in the Julian or Gregorian calendar with an intercalary day added to February (in the Gregorian calendar, February 29), used to adjust for the extra hours of the solar year; a 366-day year.

   Synonyms: bissext, bissextile, bissextile year, intercalary year

   • 1842, “CALENDAR”, in The Encyclopædia Britannica or Dictionary of Arts, Sciences, and General Literature. […], 7th edition, volume VI, Edinburgh: Adam and Charles Black, →OCLC, page 5, column 2:

     The additional day which occurred every fourth year [after the Julian Reform] was given to February, as being the shortest month, and was inserted in the calendar between the twenty-fourth and twenty-fifth day. February having then twenty-nine days, the twenty-fifth was the sixth of the calends of March, sexto calendas; the preceding, which was the additional or intercalary day, was called bis-sexto calendas, hence the term bissextile, which is still employed to distinguish the year of 366 days. The English denomination of Leap-Year would have been more appropriate if that year had differed from common years in defect, and contained only 364 days. In the ecclesiastical calendar the intercalary day is still placed between the 24th and 25th of February; in the civil calendar it is the 29th.

2. (loosely) Any other year featuring intercalation, such as a year in a lunisolar calendar with 13 months instead of 12, used to maintain its alignment with the seasons of the solar year.

• leapyear

• bissextile month
• leap day
• leap second

• common year

• leap year on Wikipedia.Wikipedia
• Douglas Harper (2001–2024) “leap year”, in Online Etymology Dictionary.