Origin Of The Gregorian Calendar: Where Does Our Current Calendar Come From?
In our daily lives we constantly use dates and record days, months, weeks, years on a daily basis. We do it with a logical automatism, since it is the calculation of time that is known to us. But this was not always so; In fact, our current calendar, The Gregorian calendar (which is our international reference) was created to rectify a miscalculation that had been accumulating for centuries If you are interested in the topic, keep reading; In today’s article we address the origins of our current calendar.
The Gregorian calendar: where does our current calendar come from?
Well, indeed, a mistake. But let’s be more explicit. The Gregorian calendar came into force on the day after October 4, 1582, by virtue of a papal bull that ordered it. Following the instructions, the 5th became October 15th, so 10 days were eliminated from the calendar This annulment led to curious situations, such as the one that originated with the death of Saint Teresa of Jesús; The saint died that same October 4 and was buried the next day… technically, October 15.
The objective of this deletion, which, a priori, may seem astonishing to us (eliminating more than a week from the calendar in one fell swoop is still striking) was none other than to rectify a calculation error that established in the calendar a lag of more than 11 minutes compared to the tropic year, that is, the astronomical year. At first glance, 11 minutes does not seem to be too serious an error. But if we add these minutes and accumulate them over centuries, the result is days of error, which are precisely those that were eliminated during the reform of the 16th century.
Prior to the establishment of the calendar that came into force in 1582 (called the Gregorian calendar after the pope who promoted it, Gregory XIII), The Christian world was governed by the so-called Julian calendar, a time calculation established by none other than Julius Caesar in the year 46 BC In the same way as what happened in the 16th century, the intention was to put an end to the multiple errors that accumulated in the Roman republican calendar, which had become a real chaos.
The errors of the old republican calendar
The Rome of the Republic followed a calendar that was quite poor in terms of astronomical accuracy, which gave the year a total of 355 days, distributed over 12 months of unequal length. Aware of the gap that this meant with respect to the tropical year, the Roman pontiffs added from time to time (without any regularity) an extra month, which they called intercalary and which usually fell after February, the end of the year in Roman times. However, this addition did not follow mathematical or constant guidelines, and was often used by leaders for their own benefit. The result was that in the time of Julius Caesar the gap with respect to the astronomical year began to be worrying
Influenced by the Egyptian calculation of time, which was governed by a solar calendar (one of the first in history), Caesar promoted the creation of a new calendar, which began to be in force in 46 BC and which was called Julian in its honor. This new calendar now had 365.25 days, which in principle was an effective solution to rectify the chaos that the old republican calendar had caused. But, in reality, the solution only entailed a new gap, as we will see.
A delay of more than 11 minutes
Those little more than 11 minutes meant nothing at first. However, over the years, they accumulated, and in the 16th century they already represented 10 days of error. This mismatch caused the seasons to start on the wrong dates, which especially affected the celebration of Christian Easter which, as we will see, was the main reason (or perhaps the only one) for the ecclesiastical authorities to decide to find a solution.
In his study The reform of the calendar. Attempts to transform the Gregorian calendar (see bibliography), Wenceslao Segura González takes a tour of the various attempts that occurred throughout history to correct the error of the Julian calendar. Because, in reality, it was not in the 16th century when scholars were aware of the gap; The error was known as early as the 4th century, although the gap was not yet large enough to cause concern.
Entering the Middle Ages it was something else. The days were adding up, and the seasonal changes were beginning to diverge. Thus, we have several reform attempts already in the 13th century; among them, that of Robert Grosseteste (1175-1253), bishop of Lincoln, who proposed changing the start day of Christian Easter from March 21 to March 15. In reality, this change meant, more than a modification of the Julian calendar, an “adaptation” of Easter to the time lag Let us remember that the only thing that mattered to the scholars was that, due to the error, the Easter liturgy was delayed too long in time.
To understand the concern raised regarding Easter, we must first be clear about how the date is calculated, which, as we know, is mobile. Christianity established that the Christian Easter should be celebrated in spring, and Easter Sunday should invariably coincide with the first full moon after the equinox (that is, after March 21). In this case, the liturgical calendar took up the Jewish witness and was based on the movements of the moon instead of those of the sun
But what happened when the lag produced by the Julian calendar began to be evident? Well, Easter never coincided exactly with what was stipulated with the Church, since the seasons moved their beginning by no less than 10 days. As Wenceslao Segura López details in the aforementioned work, if the error had not been rectified, Easter would have ended up falling in summer.
Therefore, more for religious reasons than for civil needs, The Church decided to take charge of the issue and for centuries tried, through the greatest specialists in astronomy, to repair the error that the great Caesar had left as an inheritance We have already said that various options were studied, but the solution did not arrive until the 16th century, at the hands of the so-called “Calendar Commission”.
There was a precedent from the same century, which came from the University of Salamanca. In 1515, and in response to the pope’s request to definitively find a solution to the time gap, some scholars from the University of Salamanca sent a fairly complete report, to which no one paid attention. It was not until after the Council of Trent (ended in 1563), and with the impetus of the new counter-reformist airs, that Gregory XIII finally decided to get down to work
The “Calendar Commission” was formed, among others, by the astronomers Cristóbal Clavio (1538-1612), advisor to none other than Galileo Galilei, and Luis Lilio (1510-1576). When Lilio died, the former took the reins of the Commission and modified some proposals that Lilio had made, for which he also based himself on the ignored report from the University of Salamanca. The result was what we know today as the Gregorian calendar (perhaps it should more fairly be called the Lillian or Clavian calendar), the computation of time that survives today.
What did Clavio’s definitive reforms consist of? The 365.25 days of the Julian calendar went from 365 to our current calendar and, in addition, the 10 days that had accumulated for centuries were eliminated at a stroke Technically, October 5, 1582 or October 9, 1582 never existed, and the people who went to bed on the night of the 4th got up on the morning of October 15, 1582.
The gradual acceptance of the Gregorian calendar
But the change was not automatically accepted in all territories. The first to make the calendar change were the kingdoms of the Catholic area: the Hispanic crown, Portugal, Catholic Poland and the Italian territories, which went from Thursday, October 4 to Friday, October 15. France did it a little later, as it adopted the change in transit from December 9 to December 20 of that same year 1582.
As expected, the places that showed the most reluctance were those in the Protestant area, because the change came from a papal bull. In a context of religious struggle, changing the calendar was almost the same as bending to the will of the pope, and many territories with a Protestant majority were not willing to give in Thus, Prussia and the Netherlands did not accept the Gregorian calendar until 1700, and England did so even later, in 1752.
Russia adopted the new calculation at a very late date, with the outbreak of the 1917 Revolution, called the October Revolution precisely because the empire had not yet adopted the Gregorian calendar (the rest of Europe was already in November). However, contrary to what many people believe, it was not the last territory to “convert”: the last was Greece, which switched to the new calendar in 1923.
The current Gregorian calendar is of course much more accurate than the Julian calendar, but it still presents the possibility of error, since the Earth’s rotation accumulates one day every 3,300 years. What future scholars will do back in the year 5000 to amend it, we do not know
