Gregorian calendar

2019 in various Gregorian calendar
Ab urbe condita2772
Armenian calendar1468
Assyrian calendar6769
Bahá'í calendar175–176
Balinese saka calendar1940–1941
Bengali calendar1426
Berber calendar2969
British Regnal year67 Eliz. 2 – 68 Eliz. 2
Buddhist calendar2563
Burmese calendar1381
Byzantine calendar7527–7528
Chinese calendar戊戌(Earth Dog)
4715 or 4655
    — to —
己亥年 (Earth Pig)
4716 or 4656
Coptic calendar1735–1736
Discordian calendar3185
Ethiopian calendar2011–2012
Hebrew calendar5779–5780
Hindu calendars
 - Vikram Samvat2075–2076
 - Shaka Samvat1940–1941
 - Kali Yuga5119–5120
Holocene calendar12019
Igbo calendar1019–1020
Iranian calendar1397–1398
Islamic calendar1440–1441
Japanese calendarHeisei 31 / Reiwa 1
Javanese calendar1952–1953
Juche calendar108
Julian calendarGregorian minus 13 days
Korean calendar4352
Minguo calendarROC 108
Nanakshahi calendar551
Thai solar calendar2562
Tibetan calendar阳土狗年
(male Earth-Dog)
2145 or 1764 or 992
    — to —
(female Earth-Pig)
2146 or 1765 or 993
Unix time1546300800 – 1577836799

The Gregorian calendar is the calendar used in most of the world.[1] It is named after Pope Gregory XIII, who introduced it in October 1582.

The calendar spaces leap years to make the average year 365.2425 days long, approximating the 365.2422-day tropical year that is determined by the Earth's revolution around the Sun. The rule for leap years is:

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.[2]

The calendar was developed as a correction to the Julian calendar,[Note 1] shortening the average year by 0.0075 days to stop the drift of the calendar with respect to the equinoxes.[3] To deal with the 10 days' difference (between calendar and reality) that this drift had already reached, the date was advanced so that 4 October 1582 was followed by 15 October 1582. There was no discontinuity in the cycle of weekdays or of the Anno Domini calendar era.[Note 2] The reform also altered the lunar cycle used by the Church to calculate the date for Easter (computus), restoring it to the time of the year as originally celebrated by the early Church.

The reform was adopted initially by the Catholic countries of Europe and their overseas possessions. Over the next three centuries, the Protestant and Eastern Orthodox countries also moved to what they called the Improved calendar, with Greece being the last European country to adopt the calendar in 1923.[5] To unambiguously specify a date during the transition period, (or in history texts), dual dating is sometimes used to specify both Old Style and New Style dates (abbreviated as O.S and N.S. respectively). Due to globalization in the 20th century, the calendar has also been adopted by most non-Western countries for civil purposes. The calendar era carries the alternative secular name of "Common Era".


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 with 12 months of 28–31 days each. A regular Gregorian year consists of 365 days, but in certain years known as leap years, a leap day is added to February. Gregorian years are identified by consecutive year numbers.[6] A calendar date is fully specified by the year (numbered according to a calendar era, in this case Anno Domini or Common Era), the month (identified by name or number), and the day of the month (numbered sequentially starting from 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).

In the Julian calendar, a leap year occurred every 4 years, and the leap day was inserted by doubling 24 February. The Gregorian reform omitted a leap day in three of every 400 years and left the leap day unchanged. However, it has become customary in the modern period to number the days sequentially with no gaps, 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.[7]

Calendar cycles repeat completely every 400 years, which equals 146,097 days.[Note 3][Note 4] 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 5]