Julian calendar

Gregorian20 June 2018
Julian7 June 2018

The Julian calendar, proposed by Julius Caesar in 46 BC (708 AUC), was a reform of the Roman calendar.[1] It took effect on 1 January 45 BC (AUC 709), by edict. It was the predominant calendar in the Roman world, most of Europe, and in European settlements in the Americas and elsewhere, until it was refined and gradually replaced by the Gregorian calendar, promulgated in 1582 by Pope Gregory XIII. The Julian calendar gains against the mean tropical year at the rate of one day in 128 years. For the Gregorian calendar, the figure is one day in 3,030 years.[2] The difference in the average length of the year between Julian (365.25 days) and Gregorian (365.2425 days) is 0.002%.

The Julian calendar has a regular year of 365 days divided into 12 months, as listed in the table below. A leap day is added to February every four years. The Julian year is, therefore, on average 365.25 days long. It was intended to approximate the tropical (solar) year. Although Greek astronomers had known, at least since Hipparchus, a century before the Julian reform, that the tropical year was slightly shorter than 365.25 days, the calendar did not compensate for this difference. As a result, the calendar year gains about three days every four centuries compared to observed equinox times and the seasons. This discrepancy was corrected by the Gregorian reform of 1582. The Gregorian calendar has the same months and month lengths as the Julian calendar, but, in the Gregorian calendar, years evenly divisible by 100 are not leap years, except that years evenly divisible by 400 remain leap years.[3] Consequently—since 16 February Julian/1 March 1900 Gregorian and until 15 February Julian/28 February 2100 Gregorian—the Julian calendar is currently 13 days behind the Gregorian calendar.

The Julian calendar has been replaced as the civil calendar by the Gregorian calendar in almost all countries which formerly used it, although it continued to be the civil calendar of some countries into the 20th century.[4] Egypt converted on 20 December 1874/1 January 1875. Turkey switched (for fiscal purposes) on 16 February/1 March 1917. Russia changed on 1/14 February 1918.[5] Greece made the change for civil purposes on 16 February/1 March 1923, but the national day (25 March), which was a religious holiday, was to remain on the old calendar. Most Christian denominations in the west and areas evangelised by western churches have also replaced the Julian calendar with the Gregorian as the basis for their liturgical calendars. However, most branches of the Eastern Orthodox Church still use the Julian calendar for calculating the date of Easter, upon which the timing of all the other moveable feasts depends. Some Orthodox churches have adopted the Revised Julian calendar for the observance of fixed feasts, while other Orthodox churches retain the Julian calendar for all purposes.[6] The Julian calendar is still used by the Berbers of the Maghreb in the form of the Berber calendar,[7] and on Mount Athos. In the form of the Alexandrian calendar, it is the basis for the Ethiopian calendar, which is the civil calendar of Ethiopia.

During the changeover between calendars and for some time afterwards, dual dating was used in documents and gave the date according to both systems. In contemporary as well as modern texts that describe events during the period of change, it is customary to clarify to which calendar a given date refers by using an O.S. or N.S. suffix (denoting Old Style, Julian or New Style, Gregorian).

Table of months

Months (Roman) Lengths before 45 BC Lengths as of 45 BC Months (English)
Ianuarius[8] 29 31 January
Februarius 28 (in common years)
In intercalary years:
23 if Intercalaris is variable
23/24 if Intercalaris is fixed
28 (leap years: 29) February
Martius 31 31 March
Aprilis 29 30 April
Maius 31 31 May
Iunius[8] 29 30 June
Quintilis[9] (Iulius) 31 31 July
Sextilis (Augustus) 29 31 August
September 29 30 September
October 31 31 October
November 29 30 November
December 29 31 December
Other Languages
azərbaycanca: Yuli təqvimi
Bân-lâm-gú: Julius Le̍k-hoat
башҡортса: Юлиан календары
беларуская: Юліянскі каляндар
беларуская (тарашкевіца)‎: Юліянскі каляндар
brezhoneg: Deiziadur juluan
Esperanto: Julia kalendaro
한국어: 율리우스력
Bahasa Indonesia: Kalender Julius
къарачай-малкъар: Юлиан орузлама
Kreyòl ayisyen: Almanak jilyen
Lëtzebuergesch: Julianesche Kalenner
Bahasa Melayu: Takwim Julius
Nederlands: Juliaanse kalender
日本語: ユリウス暦
Nordfriisk: Juliaans kalender
oʻzbekcha/ўзбекча: Yulian taqvimi
Simple English: Julian calendar
slovenščina: Julijanski koledar
srpskohrvatski / српскохрватски: Julijanski kalendar
Türkçe: Jülyen takvimi
ئۇيغۇرچە / Uyghurche: جۇلىيان تەقۋىمى
Tiếng Việt: Lịch Julius
吴语: 儒略曆
粵語: 儒略曆
中文: 儒略曆