Introduction
The year 1582, starting on Monday (according to Julian Calendar) but start on Friday in Gregorian Calendar. 1582 saw the start of the Gregorian Calendar switch following the Papal bull Inter Gravissimas issued by the a pope of the Catholic Church. The Gregorian Calendar has been adopted by Spain, Portugal, the Polish-Lithuanian Commonwealth and present-day Italy. In most countries, the year continued as normal from Thursday, October 4; the next day became Friday, October 15, just like a startup of anew year starting on Friday. France followed two months later, letting Sunday, December 9 be followed by Monday, December 20. however, the complete conversion of the Gregorian calendar was entirely reinforced in 1923.
Pope Gregory XIII
Born on the (7th of January, 1502 - 10th of April 1585) as Ugo Boncompagni, Gregory made many contributions to the life of the Catholic Church, the city of Rome, education, arts and diplomacy.
Before ascending to the papacy, Boncompagni had a distinguished career in law in Bologna where he received his doctorate in both civil and canon law. He also taught jurisprudence, which is the theory and philosophy of law.
His intellectual influence positioned him as a trusted figure in legal and diplomatic circles even before his election as pope in the 1572 conclave. Upon being elected he adopted the name Gregory, in honour of Pope Gregory the Great who lived in the sixth century.
Reason of the diversion
The pope issued the bull (a formal proclamation), known by its first Latin words as Inter Gravissimas, on February 24, 1582. Its aim was to reform the Julian calendar’s method of calculating the date of Easter, which had been standardized in 325 at the First Council of Nicaea, a meeting of Christian bishops that, in turn, had largely followed precepts laid down at the First Council of Arles (314). These early councils established rules to set the date of the moveable feast of Easter based on an assumption that the solar year lasts 365.25 days, an overestimation of about eleven minutes. This astronomical mistake had religious implications because it meant that over time the calendar and the seasons became misaligned. As Easter came later in the year at a rate of about one day every 130 years, the pope worried that other holidays fixed to Easter—for example the Pentecost, or Whitsunday, on the seventh Sunday following Easter—might collide with pagan festivals such as the summer solstice.
To rectify this problem, Gregory ordered churches to drop ten days from that year’s calendar, so that Thursday, October 4, 1582, was followed by Friday, October 15. (The pope chose October because it was a month with few holidays or official conflicts in the church.) He also instituted a new system of fewer leap, or extra, days. Rather than adding a day to the month of February every four years, as the Julian calendar did, the system would add a leap day only in those years whose numbers can be evenly divided by 4, the exception being those years that are also divisible by 100, unless they are also divisible by 400 (for example, the year 1600).
Much of Catholic Europe quickly aligned its calendars according to Gregory’s decree. Spain, Portugal, Poland, and most of Italy did so in October 1582; France and the Spanish Netherlands in December 1582; Austria in 1583; Bohemia and Moravia in January 1584; Hungary in 1587; and, a bit later, Prussia in 1610. Protestant countries such as England and Scotland, which did not recognize the pope’s authority, did not, therefore, immediately adopt the Gregorian calendar. John Dee, a geographer and mathematician who advised Queen Elizabeth I, devised a more scientifically exact calendar than Pope Gregory’s, but it never gained widespread use.
In the meantime, most of the Catholic countries, even before accepting the Gregorian reform, dated their new year from January 1. (The church began its ecclesiastical calendar at Christmas, but still celebrated a feast day on January 1.) While remaining on the Julian calendar, Scotland adopted January 1 as the beginning of the new year in 1600. England, by contrast, began its year with the Feast of the Annunciation, known in England as Lady Day and celebrated on March 25. With the Act of Union (1707) joining England and Scotland, these date disparities created a problem. The old ten-day disparity between the Old Style calendar and the seasons had grown, by this time, to eleven days (1700 was a leap year under the Julian, but not the Gregorian, calendar), so that, according to the historian Duncan Steel, a given day might be reflected by as many as three different dates: “February 1, 1720, in Scotland, February 1, 1719, in England, and February 12, 1720, in most of the rest of Europe.”
To acknowledge these differences, many correspondents and publications, including some in Virginia, took to assigning two years—Old Style and New Style—with dates that occurred between January 1 and March 25 in the years after 1582. That practice ceased when Great Britain adopted the Gregorian calendar in 1752. Two years earlier, Parliament had passed “An act for regulating the commencement of the year; and for correcting the calendar now in use.” Known as the Calendar (New Style) Act, it directed that the year 1751 would end on December 31 and the year 1752 would begin on January 1. Additionally, Wednesday, September 2, 1752, should be followed by Thursday, September 14, 1752.
Other Actors involved in the introduction of the Gregorian Calendar
Aloysius Lilius
He is primarily known as the inventor of the Gregorian Calendar: he wrote the proposal on which (after modifications) the calendar reform was based. Lilio's brother Antonio presented the manuscript to Pope Gregory XIII; it was passed to the calendar reform commission in 1575. The commission issued a printed summary entitled Compendium novae rationis restituendi kalendarium (Compendium of a New Plan for the Restitution of the Calendar), printed in 1577 and circulated within the Roman Catholic world in early 1578 as a consultation document. Lilio's manuscript itself is not known to have survived; the printed Compendium is the nearest known source for the details it contained.
The processes of consultation and deliberation meant that the reform to the calendar did not occur until 1582, six years after the death of Luigi Lilio in 1576. The reform had by then received some modifications in points of detail by the reform commission, in which one of the leading members was Christopher Clavius, who afterwards wrote defences and an explanation of the reformed calendar, including an emphatic acknowledgement of Lilio's work, especially for his provision of a useful reform for the lunar cycle: "We owe much gratitude and praise to Luigi Giglio who contrived such an ingenious Cycle of Epacts which, inserted in the calendar, always shows the new moon and so can be easily adapted to any length of the year, if only at the right moments the due adjustment is applied."
Christopher Clavius
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Christopher Clavius, (25 March 1538 – 6 February 1612) was a Jesuit German mathematician, head of mathematicians at the Collegio Romano, and astronomer who was a member of the Vatican commission that accepted the proposed calendar invented by Aloysius Lilius, that is known as the Gregorian calendar. Clavius would later write defences and an explanation of the reformed calendar, including an emphatic acknowledgement of Lilius' work. In his last years he was probably the most respected astronomer in Europe and his textbooks were used for astronomical education for over fifty years in and even out of Europe.
ACKNOWLEDGEMENT
I want to express my heartfelt gratitude and appreciation to all websites (Wikipedia and Britannica) that have contributed to the successful completion of this research blog.
A big thanks to my brother, Mr. Badmus, Jamiu Olamilekan for his guidance and support. His expertise and mentorship have been instrumental in shaping this research blog and motivating me toward excellence.
Also, a big shoutout to everyone that has dedicate their time reading this research blog.