We explain what the Julian calendar is and who it is named after. Also, its characteristics and the causes of its replacement.
What is the Julian calendar?
The Julian calendar It was the predominant temporal order system in Europe between the 1st centuries BC. C and XVI d. c It was introduced by Julius Caesar in ancient Rome in 46 BC. C. and remained in force until, between the 16th and 18th centuries, the Gregorian calendar that is used today was introduced.
The Julian calendar divided the year into 365 days and added one day every four years. That is, every four years there was a “leap year” that had 366 days. Julius Caesar's objective was to fix the temporal organization that Rome had until then, based on different calendars, which had produced a mismatch between the natural seasons and the civil calendar.
See also: Roman Empire
History of the Julian calendar
Before the reform introduced by Julius Caesar, ancient Rome It was governed based on a calendar of 304 days, distributed over ten months. This organization generated irregularities and gaps that were corrected according to the economic and political needs of the moment.
The Julian calendar established that the solar year had a total duration of 365.25 days. Therefore, the regular year of 365 days over twelve months was created, with a leap day introduced between February 23 and 24 every four years.
To correct the large gap produced by the previous calendar system, An intermediate year was introduced between the use of that calendar and the new system. That year is known as the “year of confusion” and had 445 days.
The Julian calendar It was created by an Alexandrian astronomer named Sosigenes. His original proposal divided the year into twelve months: Januarius, Februarius, Martius, Aprilis, Maius, Junius, Quintilis, Sextilis, September, October, November and December. The odd-numbered months had 31 days and the even-numbered months had 30, except for Februarius which had 29.
However, Julius Caesar changed the name of the month of his birth, Quintilis, to Julius. And a few years later, Emperor Augustus did the same, and the month of Sextilis was renamed Augustus.
Furthermore, since Emperor Augustus did not want “his” month to last less than Julius Caesar's, he made Augustus have 31 days. And then, so that there are not three months in a row of 31 days, made a modification to the monthly calendar organization that lasts until today.
Features of the Julian calendar
After the implementation of the Julian calendar and its first reforms, The year was divided into the following months:
- Januarius: 31 days.
- Februarius: 28 days (+1 each leap year).
- Martius: 31 days.
- Aprilis: 30 days.
- Maius: 31 days.
- Junius: 30 days.
- Julius: 31 days.
- Augustus: 31 days.
- September: 30 days.
- October: 31 days.
- November: 30 days.
- December: 31 days.
In turn, within the months of the Julian calendar, phases were differentiated in relation to the lunar calendar:
- The Kalends They were the first days of each month and corresponded to the phase of the new Moon.
- The Nonas. They were days 5 or 7 (depending on the number of days in each month) and corresponded to the crescent moon phase.
- The Ides. They were the 13th or 15th (according to the Nones) and corresponded to the full Moon.
Why is a year with 366 days called a “leap year”?
In the Julian calendar, the last day of Februarius was called ante diem sextum calends Martius (which in Latin means “the sixth day before the calends of Martius”). And the day that was added to the calendar every four years was the one immediately after the sextumTherefore, it was called bis-sextum. That's where the name “leap year” comes from.
Julian calendar problem
The calculations made by Sosigenes in the 1st century BC. c. established the total length of the year at 365.25 days. This number is very close to the actual duration of the tropical year (how long it takes for the Sun to pass through the same point again from the Earth's point of view), as the Gregorian calendar (which replaced the Julian calendar in the 16th century). calculated at 365.2422 days.
The difference between one and the other is 11 minutes and 28 seconds. This small difference generated one day of lag every 128 years and, over the centuries, produced a displacement of the civil calendar with respect to the seasons which became very evident.
On the other hand, this gap generated problems in the organization of the liturgical calendar (the religious calendar) of the Catholic Church. Christians had established at the Council of Nicaea (325 AD) the celebration of Easter and other festivities in relation to a lunisolar system (that is, one that took into account the Julian solar calendar and the phases of the moon) and the dates of the spring and autumn equinoxes.
For this reason, in the 16th century, The Council of Trent defined the need to adjust the calendar. In 1582, Pope Gregory XIII postulated a reform based on the astronomical studies of Cristóbal Clavio, Luis Lilio and Pedro Chacón. This new system replaced the use of the Julian calendar in different parts of Europe between the 16th and 18th centuries.
References
- Gutiérrez, S. (2008). Our calendar: a highly precise measure. Addition (pp. 87-92).
- Llagostera Cuenca, E. (2007). The measurement of time in Antiquity: the Egyptian calendar and its “heirs”, the Julian and the Gregorian. UNED. Space, Time and Form Series II, Ancient History.
- Vicente, JJ (2010). Brief history of the calendar. Astronomy (pp. 69-86). University of Granada.
