calendar introduced by Julius Caesar in 45 BC From Wikipedia, the free encyclopedia
The Julian calendar, proposed by Julius Caesar in 46 BCE (708 AUC), was a reform of the Roman calendar.[1] It was first used in 1 January 45 BCE. It was the main calendar in most of the world, until Pope Gregory XIII replaced that with the Gregorian calendar in 4 October 1582.
During the 20th and 21st centuries, the date according to the Julian calendar is 13 days behind the Gregorian date.
The Julian calendar has two types of year: common years of 365 days and leap years of 366 days. There is a simple cycle of three common years followed by a leap year and this pattern repeats forever. However, the rule was not followed in the first years after the reform in 45 BCE. Due to a counting error, every 3rd year was a leap year instead of the 4th. The leap years were:[2]
However, in 8 BCE (746 AUC), emperor Augustus Caesar corrected the problem. The next leap year was 7 CE (160 AUC).
With the simple cycle, the length of the Julian year is exactly 365.25 days (365 days and 6 hours), but the actual time it takes for the Earth to go around the Sun once is closer to 365.2422 days (about 365 days, 5 hours, 48 minutes and 46 seconds). This difference is about 365.25 - 365.2422 = 0.0078 days (11 minutes and 14 seconds) each year, although Greek astronomers knew that.[3] This made the seasons get out of track, since the real first day of spring in western Europe (the equinox - day and night the same length) was happening earlier and earlier before the traditional 21 March as the centuries went by. By the 1500s, it was starting around 11 March, ten days 'too early' according to the calendar.
The first step of the reform was to realign the 25 December with the Winter solstice by making 46 BCE (708 AUC) 445 days long. In ordinary Roman calendar, the common year had 355 days and the leap year (one year after the common year) had 378 days. The 46 BCE was a leap year, according to the calendar. Julius Caesar added 67 more days by adding two extra months (those are called Prior and Posterior in letters of Cicero) between November and December.
Months | 47 BCE (707 AUC) |
46 BCE (708 AUC) |
45 BCE (709 AUC) |
8 BCE (746 AUC) |
---|---|---|---|---|
January | 29 | 29 | 31 | 31 |
February | 28 | 24 | 30 | 28 |
Intercalaris | 27 | |||
March | 31 | 31 | 31 | 31 |
April | 29 | 29 | 30 | 30 |
May | 31 | 31 | 31 | 31 |
June | 29 | 29 | 30 | 30 |
Quintilis | 31 | 31 | 31 | 31 |
Sextilis | 29 | 29 | 30 | 31 |
September | 29 | 29 | 30 | 30 |
October | 31 | 31 | 31 | 31 |
November | 29 | 29 | 30 | 30 |
Prior | 33 | |||
Posterior | 34 | |||
December | 29 | 29 | 31 | 31 |
Total | 355 | 445 | 366 | 365 |
Seamless Wikipedia browsing. On steroids.
Every time you click a link to Wikipedia, Wiktionary or Wikiquote in your browser's search results, it will show the modern Wikiwand interface.
Wikiwand extension is a five stars, simple, with minimum permission required to keep your browsing private, safe and transparent.