Julian calendar

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2019 in various calendars
Gregorian calendar2019
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Armenian calendar1468
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Bahá'í calendar175–176
Balinese saka calendar1940–1941
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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
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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 Julian calendar is a calendar that was invented by Julius Caesar, the leader of Ancient Rome. It is a reform of the Roman calendar. It was first used in the year 709 AUC (45 BC). Caesar consulted the astronomer Sosigenes of Alexandria. Very probably it was made to approximate the tropical year, which was known at least since Hipparchus.

The calendar has two types of year: regular years of 365 days divided into 12 months and leap years of 366 days. There is a simple cycle of three regular years followed by a leap year and this cycle repeats forever. The Julian year is, therefore, on average 365.25 days long. But in reality, the Earth moves around the Sun about 365.24217 days.

In the 16th century, the Gregorian calendar was introduced in Europe because the Julian Calendar makes too many leap days, which means that it gains a day about every 128 years. The Gregorian calendar has 97 leap days every 400 years, while the Julian had exactly 100. People sometimes use the term Old Style or O.S. to refer to the Julian calendar, with N.S. or New Style referring to the Gregorian calendar. During the 20th and 21st centuries, the O.S. date is 13 days behind the N.S. date.

Some countries used this calendar to the 20th century. Mount Athos, and many national Eastern Orthodox churches still use the Julian calendar, or a revised form, introduced in 1923.

Table of months[change | change source]

This table compares between Roman calendar and Julian calendar
Months (Roman) Lengths before 45 BC Lengths as of 45 BC Months (English)
Ianuarius[1] 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[1] 29 30 June
Quintilis[2] (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

References[change | change source]

  1. 1.0 1.1 The letter J was not invented until the 16th century.
  2. The spelling Quinctilis is also used; see page 669 of The Oxford Companion to the Year.

Related pages[change | change source]