Gregorian calendar

2018 in various calendars
Gregorian calendar 2018
Ab urbe condita 2771
Armenian calendar 1467
Assyrian calendar 6768
Bahá'í calendar 174–175
Balinese saka calendar 1939–1940
Bengali calendar 1425
Berber calendar 2968
British Regnal year 66  Eliz. 2 – 67  Eliz. 2
Buddhist calendar 2562
Burmese calendar 1380
Byzantine calendar 7526–7527
Chinese calendar 丁酉(Fire  Rooster)
4714 or 4654
    — to —
戊戌年 (Earth  Dog)
4715 or 4655
Coptic calendar 1734–1735
Discordian calendar 3184
Ethiopian calendar 2010–2011
Hebrew calendar 5778–5779
Hindu calendars
 - Vikram Samvat 2074–2075
 - Shaka Samvat 1939–1940
 - Kali Yuga 5118–5119
Holocene calendar 12018
Igbo calendar 1018–1019
Iranian calendar 1396–1397
Islamic calendar 1439–1440
Japanese calendar Heisei 30
Javanese calendar 1951–1952
Juche calendar 107
Julian calendar Gregorian minus 13 days
Korean calendar 4351
Minguo calendar ROC 107
Nanakshahi calendar 550
Thai solar calendar 2561
Tibetan calendar 阴火鸡年
(female Fire- Rooster)
2144 or 1763 or 991
    — to —
(male Earth- Dog)
2145 or 1764 or 992
Unix time 1514764800 – 1546300799

The Gregorian calendar is internationally the most widely used civil calendar. [1] [2] [Note 1] It is named after Pope Gregory XIII, who introduced it in October 1582.

It was a refinement to the Julian calendar [3] involving an approximately 0.002% correction in the length of the calendar year. The motivation for the reform was to stop the drift of the calendar with respect to the equinoxes and solstices—particularly the northern vernal equinox, which helps set the date for Easter. Transition to the Gregorian calendar would restore the holiday to the time of the year in which it was celebrated when introduced by the early Church. The reform was adopted initially by the Catholic countries of Europe. Protestants and Eastern Orthodox countries continued to use the traditional Julian calendar and adopted the Gregorian reform, one by one, after a time, at least for civil purposes and for the sake of convenience in international trade. The last European country to adopt the reform was Greece, in 1923. Many (but not all) countries that have traditionally used the Julian calendar, or the Islamic or other religious calendars, have come to adopt the Gregorian calendar for civil purposes.

The Gregorian reform contained two parts: a reform of the Julian calendar as used prior to Pope Gregory XIII's time, and a reform of the lunar cycle used by the Church with the Julian calendar to calculate the date of Easter. The reform was a modification of a proposal made by Aloysius Lilius, [4] who proposed to reduce the number of leap years that occur in every four centuries from 100 to 97, by making 3 out of 4 centurial years common years instead of leap years. Lilius also produced an original and practical scheme for adjusting the epacts of the moon when calculating the annual date of Easter, solving a long-standing obstacle to calendar reform.

The Gregorian reform modified the Julian calendar's scheme of leap years as follows:

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 are not leap years, but the year 2000 is. [5]

In addition to the change in the mean length of the calendar year from 365.25 days (365 days 6 hours) to 365.2425 days (365 days 5 hours 49 minutes 12 seconds), a reduction of 10 minutes 48 seconds per year, the Gregorian calendar reform also dealt with the accumulated difference between these lengths. The canonical Easter tables were devised at the end of the third century, when the vernal equinox fell either on 20 March or 21 March depending on the year's position in the leap year cycle. As the rule was that the full moon preceding Easter was not to precede the equinox, the date was fixed at 21 March for computational purposes and the earliest date for Easter was fixed at 22 March. The Gregorian calendar reproduced these conditions by removing ten days. [6]

To unambiguously specify a date, dual dating or Old Style and New Style dates are sometimes used. Dual dating gives two consecutive years for a given date because of differences in the starting date of the year or to give both the Julian and the Gregorian dates. The "Old Style" (O.S.) and "New Style" (N.S.) notations indicate either that the start of the Julian year has (or has not) been adjusted to start on 1 January (even though documents written at the time use a different start of year), or that a date conforms to the (old) Julian calendar rather than the (new) Gregorian. [Note 2]

The Gregorian calendar continued to use the previous calendar era (year-numbering system), which counts years from the traditional date of the nativity ( Anno Domini), originally calculated in the 6th century by Dionysius Exiguus. [7] This year-numbering system, also known as Dionysian era or Common Era, is the predominant international standard today. [Note 3]


A year is divided into twelve months
No. Name Length in days
1 January 31
2 February 28 (29 in leap years)
3 March 31
4 April 30
5 May 31
6 June 30
7 July 31
8 August 31
9 September 30
10 October 31
11 November 30
12 December 31

The Gregorian calendar is a solar calendar. A regular Gregorian year consists of 365 days, but as in the Julian calendar, in certain years, a leap year, a leap day is added to February. In the Julian calendar a leap year occurs every 4 years, but the Gregorian calendar omits a leap day in three of every 400 years. In the Julian calendar, the leap day was inserted by doubling 24 February, and the Gregorian reform did not change the date of the leap day. In the modern period, it has become customary to number the days from the beginning of the month, and 29 February is typically considered as the leap day. Before the 1969 revision of the Roman Calendar, the Roman Catholic Church delayed February feasts after the 23rd by one day in leap years; Masses celebrated according to the previous calendar still reflect this delay. [9]

Gregorian years are identified by consecutive year numbers. [10] The cycles repeat completely every 146,097 days, which equals 400 years. [Note 4] [Note 5] Of these 400 years, 303 are regular years of 365 days and 97 are leap years of 366 days. A mean calendar year is 365 97/400 days = 365.2425 days, or 365 days, 5 hours, 49 minutes and 12 seconds. [Note 6]

A calendar date is fully specified by the year (numbered by some scheme beyond the scope of the calendar itself), the month (identified by name or number), and the day of the month (numbered sequentially starting at 1). Although the calendar year currently runs from 1 January to 31 December, at previous times year numbers were based on a different starting point within the calendar (see the "beginning of the year" section below).

Other Languages
العربية: تقويم ميلادي
azərbaycanca: Qriqori təqvimi
Bân-lâm-gú: Gregorius Le̍k-hoat
Basa Banyumasan: Kalendher Gregorian
беларуская (тарашкевіца)‎: Грыгарыянскі каляндар
Chavacano de Zamboanga: Calendario Gregoriano
ދިވެހިބަސް: މީލާދީ ކަލަންޑަރު
dolnoserbski: Gregorjaniska pratyja
emiliàn e rumagnòl: Lunâri Gregoriân
客家語/Hak-kâ-ngî: Gregorius La̍k-fap
한국어: 그레고리력
hornjoserbsce: Gregorianiska protyka
বিষ্ণুপ্রিয়া মণিপুরী: গ্রেগরিয়ান পাঞ্জী
Bahasa Indonesia: Kalender Gregorius
къарачай-малкъар: Григориан орузлама
kernowek: Calans gregorek
Kreyòl ayisyen: Almanak gregoryen
Lëtzebuergesch: Gregorianesche Kalenner
مازِرونی: میلادی تقویم
Bahasa Melayu: Takwim Gregorius
Mìng-dĕ̤ng-ngṳ̄: Gregorius Lĭk-huák
Nedersaksies: Gregoriaanse kalender
oʻzbekcha/ўзбекча: Grigoriy taqvimi
Plattdüütsch: Gregoriaansch Klenner
Gagana Samoa: Kalena Kurekoria
Sesotho sa Leboa: Tšhupamabaka ya Gregorian
Simple English: Gregorian calendar
slovenščina: Gregorijanski koledar
srpskohrvatski / српскохрватски: Gregorijanski kalendar
Basa Sunda: Kalénder Grégori
татарча/tatarça: Милади тәкъвим
Türkçe: Miladi takvim
Tiếng Việt: Lịch Gregorius
文言: 格里曆
吴语: 公曆
粵語: 公曆
中文: 公历