## Leap year |

A **leap year** (also known as an **intercalary year** or **bissextile year**) is a ^{[1]} Because seasons and astronomical events do not repeat in a * intercalating*) an additional day or month into the year, the drift can be corrected. A year that is not a leap year is called a common year.

For example, in the

The name "leap year" probably comes from the fact that while a fixed date in the Gregorian calendar normally advances one day of the week from one year to the next, the day of the week in the 12 months following the leap day (from March 1 through February 28 of the following year) will advance two days due to the extra day (thus "leaping over" one of the days in the week).^{[2]}^{[3]} For example,

The length of a day is also occasionally changed by the insertion of

- gregorian calendar
- julian, coptic and ethiopian calendars
- revised julian calendar
- chinese calendar
- hebrew calendar
- islamic calendar
- hindu calendar
- bahá'í calendar
- solar hijri calendar
- folk traditions
- birthdays
- see also
- references
- external links

In the Gregorian calendar, the standard calendar in most of the world, most years that are multiples of 4 are leap years. In each leap year, the month of February has 29 days instead of 28. Adding one extra day in the calendar every four years compensates for the fact that a period of 365 days is shorter than a ^{[4]} Some exceptions to this basic rule are required since the duration of a tropical year is slightly less than 365.25 days. The

Every year that is exactly divisible by four is a leap year, except for years that are exactly divisible by 100, but these centurial years are leap years if they are exactly divisible by 400. For example, the years 1700, 1800, and 1900 were not leap years, but the years 1600 and 2000 were.

^{[5]}

Over a period of four centuries, the accumulated error of adding a leap day *every* four years amounts to about three extra days. The Gregorian calendar therefore removes three leap days every 400 years, which is the length of its *leap cycle*. This is done by removing February 29 in the three century years (multiples of 100) that cannot be exactly divided by 400.^{[6]}^{[7]} The years 1600, 2000 and 2400 are leap years, while 1700, 1800, 1900, 2100, 2200 and 2300 are common years. By this rule, the average number of days per year is 365 + ^{1}⁄_{4} − ^{1}⁄_{100} + ^{1}⁄_{400} = 365.2425.^{[8]} The rule can be applied to years before the Gregorian reform (the ^{[9]}

This graph shows the variations in date and time of the |

The Gregorian calendar was designed to keep the ^{[10]}^{[8]} The "

The following *leap year* or a *common year* in the Gregorian calendar (and in the proleptic Gregorian calendar before 1582). The *year* variable being tested is the integer representing the number of the year in the Gregorian calendar, and the tests are arranged to dispatch the most common cases first. Care should be taken in translating mathematical integer divisibility into specific programming languages.

**if** (*year* is not **then** (it is a common year)

**else if** (*year* is not divisible by 100) **then** (it is a leap year)

**else if** (*year* is not divisible by 400) **then** (it is a common year)

**else** (it is a leap year)

The algorithm is not necessarily valid for years in the Julian calendar, such as years before 1752 in the British Empire. The year 1700 was a leap year in the Julian calendar, but not in the Gregorian calendar.

February 29 is a date that usually occurs every four years, and is called leap day. This day is added to the calendar in leap years as a corrective measure, because the Earth does not orbit the sun in precisely 365 days.

The Gregorian calendar is a modification of the *Kalendae* or calends, hence "calendar") and the full moon (*Idus* or ides). The *Nonae* or nones was not the first *nundina* or Roman market week of nine days before the ides, inclusively counting the ides as the first of those nine days. This is what we would call a period of eight days. In 1825, *ante diem sextum Kalendas Martias* ("the sixth day before the calends of March") often abbreviated a. d. VI Kal. Mart. ^{[11]}

The Republican calendar's intercalary month was inserted on the first or second day after the

The Julian calendar, which was developed in 46 BC by *ante diem sextum Kalendas Martias* (February 24) was doubled, producing *ante diem bis sextum Kalendas Martias*. Hence, the year containing the doubled day was a bissextile (*bis sextum*, "twice sixth") year. For legal purposes, the two days of the *bis sextum* were considered to be a single day, with the second half being intercalated; but in common practice by 238, when *first* half of the doubled day. Thus the intercalated day was effectively inserted between the 23rd and 24th days of February. All later writers, including

Until 1970, the

The Revised

The

Other Languages

Afrikaans: Skrikkeljaar

Alemannisch: Schaltjahr

Ænglisc: Bises

العربية: سنة كبيسة

ܐܪܡܝܐ: ܫܢܬܐ ܟܒܝܫܬܐ

অসমীয়া: অধিবৰ্ষ

asturianu: Añu bisiestu

авар: Високоснияб сон

azərbaycanca: Uzun il

বাংলা: অধিবর্ষ

Bân-lâm-gú: Lūn-nî

башҡортса: Кәбисә йыл

беларуская: Высакосны год

беларуская (тарашкевіца): Высакосны год

भोजपुरी: अधिबरिस

български: Високосна година

Boarisch: Schoitjoa

bosanski: Prestupna godina

brezhoneg: Bloavezh bizeost

català: Any de traspàs

čeština: Přestupný rok

corsu: Annata bisesta

Cymraeg: Blwyddyn naid

dansk: Skudår

davvisámegiella: Gárgádusjahki

Deutsch: Schaltjahr

dolnoserbski: Pśestupne lěto

eesti: Liigaasta

Ελληνικά: Δίσεκτο έτος

español: Año bisiesto

Esperanto: Superjaro

euskara: Bisurte

فارسی: سال کبیسه

føroyskt: Leypár

français: Année bissextile

Frysk: Skrikkeljier

furlan: An bisest

Gaeilge: Bliain bhisigh

Gàidhlig: Bliadhna-leum

galego: Ano bisesto

贛語: 閏年

ગુજરાતી: લિપ વર્ષ

客家語/Hak-kâ-ngî: Yun-ngièn

хальмг: Немсән җил

한국어: 윤년

Հայերեն: Նահանջ տարի

हिन्दी: अधिवर्ष

hornjoserbsce: Přestupne lěto

hrvatski: Prijestupna godina

Ido: Bisextila yaro

Ilokano: Bisiesto a tawen

Bahasa Indonesia: Tahun kabisat

interlingua: Anno bissextil

íslenska: Hlaupár

italiano: Anno bisestile

עברית: שנה מעוברת

Basa Jawa: Taun wuntu

kalaallisut: Ukioq ilassutilik

ಕನ್ನಡ: ಅಧಿಕ ವರ್ಷ

ქართული: ნაკიანი წელიწადი

қазақша: Кібісе жылы

kernowek: Bledhen lamm

коми: Кассяна во

Kreyòl ayisyen: Bisektil

kurdî: Sala duşeşî

лезги: Яргъи йис

Latina: Annus intercalarius

latviešu: Garais gads

Lëtzebuergesch: Schaltjoer

lietuvių: Keliamieji metai

Limburgs: Sjrikkeljaor

magyar: Szökőév

मैथिली: अधिक वर्ष

македонски: Престапна година

മലയാളം: അധിവർഷം

Māori: Tau pekerangi

मराठी: लीप वर्ष

მარგალური: ნარკი წანმოწანა

مصرى: سنه كبيسه

Bahasa Melayu: Tahun lompat

Mìng-dĕ̤ng-ngṳ̄: Nông-nièng

монгол: Өндөр жил

မြန်မာဘာသာ: ရက်ထပ်နှစ်

Nāhuatl: Huēytlaōntic xihuitl

Nederlands: Schrikkeljaar

नेपाली: अधिक वर्ष

नेपाल भाषा: लीप दँ

日本語: 閏年

нохчийн: Високосан шо

Nordfriisk: Skregeljuar

norsk: Skuddår

norsk nynorsk: Skotår

occitan: Annada bissextila

oʻzbekcha/ўзбекча: Kabisa yili

ਪੰਜਾਬੀ: ਲੀਪ ਸਾਲ

Plattdüütsch: Schaltjohr

polski: Rok przestępny

português: Ano bissexto

Ripoarisch: Schalldtjoohr

română: An bisect

Runa Simi: Wakllanwata

русиньскый: Переступный рік

русский: Високосный год

Gagana Samoa: Puna ifo tausaga

संस्कृतम्: अधिवर्षम्

Scots: Leap year

Sesotho sa Leboa: Ngwagamolele

shqip: Viti i brishtë

සිංහල: අධික අවුරුද්ද

Simple English: Leap year

سنڌي: ليپ سال

slovenčina: Priestupný rok

slovenščina: Prestopno leto

Soomaaliga: Sanad Maalin Dheer

کوردی: ساڵی پڕ

српски / srpski: Преступна година

srpskohrvatski / српскохрватски: Prijestupna godina

Basa Sunda: Taun kabisat

svenska: Skottår

Tagalog: Taong bisyesto

தமிழ்: நெட்டாண்டு

татарча/tatarça: Кәбисә ел

తెలుగు: లీపు సంవత్సరము

ไทย: ปีอธิกสุรทิน

тоҷикӣ: Соли кабиса

Türkçe: Artık yıl

українська: Високосний рік

اردو: لیپ کا سال

ئۇيغۇرچە / Uyghurche: كەبىسە يىلى

Vahcuengh: Bi'nyinh

vèneto: Ano bixesto

Tiếng Việt: Năm nhuận

Võro: Liigaastak

walon: Anêye bizete

吴语: 闰年

ייִדיש: עיבור יאר

Yorùbá: Ọdún Tódọ́gba

粵語: 閏年

žemaitėška: Kelamė̄jė metā

中文: 闰年

Kabɩyɛ: Nabʊlɛ ɖeyi ɖeyi tɛyʊ pɩnaɣ