Table of contents:
- Why was the calendar reform needed?
- Caesar fixes calendar confusion
- Julian calendar
- Gregorian calendar
Most of the world has been reckoning time for four centuries using a calendar called the Gregorian. The year of this calendar is divided into 12 months and lasts 365 days. One additional day is added every four years. Such a year is called a leap year. This is necessary in order to remove the difference between the movement of the sun and the calendar.
This concept was introduced in the late 16th century by Pope Gregory XIII as a reform of the Julian calendar. The Gregorian calendar is generally accepted because it is regular and very simple. But it was not always so.
Why was the calendar reform needed?
Before the adoption of the Gregorian calendar, another was in effect - the Julian one. It was closest to the real solar calendar. Since the Earth needs a little more than exactly 365 days to make a revolution around the sun. This difference was offset by leap years.
It was an incredibly useful and large-scale reform for its time, but this calendar still could not boast of absolute accuracy. The sun makes a revolution for 11.5 minutes longer. It may seem like a trifle, but time has been slowly accumulating. Years passed, and by the 16th century the Julian calendar was ahead of the main luminary by almost eleven days.
Caesar fixes calendar confusion
The Julian calendar was introduced by the Roman emperor Julius Caesar. It happened in 46 BC. This was not a whim at all, but an attempt to correct the errors of the lunisolar calendar, which formed the basis of the current Roman one. It had 355 days, divided by 12 months, which was shorter than the solar year by as much as 10 days. To correct this discrepancy, the Romans added 22 or 23 days to each subsequent year. That is, a leap year was already a necessity. Thus, the year in Rome could last 355, 377 or 378 days.
What is even more inconvenient, leap days or the so-called intercalary days were not added according to some system, but were determined by the high priest of the College of Pontiffs. Here the negative human factor came into play. The pontiff, using his power over time, extended or shortened the year in pursuit of personal plitical goals. The end result of all this disgrace was that the Roman man in the street had no idea what day it was.
To put all this calendar chaos in order, Caesar called on the best philosophers and mathematicians of the empire. He challenged them to create a calendar that would synchronize with the sun itself, without requiring human intervention. According to the calculations of scientists of that time, the year lasted 365 days and 6 hours. Caesar's task resulted in a 365-day calendar with an extra day added every four years. This was necessary in order to compensate for the 6 lost hours every year.
Modern science clarifies that it takes our planet 365 days, 5 hours, 48 minutes and 45 seconds to go around the Sun once. That is, the newly made calendar was also not accurate. Nevertheless, it was indeed a large-scale reform. Especially compared to the then existing calendar system, which was just a messy mess.
Julius Caesar wished that the new year according to the new calendar began on January 1, and not in March. To this end, the emperor added a full 67 days to 46 BC. Because of this, it lasted a whopping 445 days! Caesar declared it "the last year of confusion", but people simply called it "the year of confusion" or annus confusionis.
According to the Julian calendar, New Year began on January 1, 45 BC.Just a year later, Julius Caesar was killed in a conspiracy. His comrade-in-arms Mark Anthony, in order to honor the memory of the great ruler, changed the name of the Roman month of Quintilis to Julius (July). Later, in honor of another Roman emperor, the month of sextilis was renamed to August.
The Julian calendar was certainly at one time a real revolution in the history of human civilization. His shortcomings began to appear over time. As mentioned above, by the end of the 16th century, it was ahead of the sun by almost 11 days. The Catholic Church considered this an unacceptable difference that needed to be corrected. This was done in 1582. The then Pope Gregory XIII issued his famous bull Inter gravissimas - about the transition to a new calendar. It was called Gregorian.
According to this decree, in 1582 the inhabitants of Rome went to bed on October 4, and woke up the next day - October 15. The count of days was moved 10 days ahead, and the day after Thursday, October 4, was prescribed to be considered Friday, but not October 5, but October 15. The order of chronology was established, in which the equinox and full moon were restored and in the future should not shift in time.
The difficult problem was solved thanks to the project of the Italian physician, astronomer and mathematician Luigi Lillio. He suggested throwing out 3 days every 400 years. Thus, instead of a hundred leap days for every 400 years in the Julian calendar, there are 97 of them left in the Gregorian calendar. Those secular years (with two zeros at the end) were excluded from the category of leap days, the number of hundreds of which is not evenly divisible by 4. Such years, in in particular, were 1700, 1800 and 1900.
The new calendar was introduced gradually in different countries. It became generally accepted by the middle of the 20th century. Almost everyone used it. In Russia, it was introduced after the October Revolution by decree of the Council of People's Commissars of the RSFSR of January 24, 1918. The Gregorian calendar was named "new style", and the Julian calendar - "old style".