Showing posts with label Gregorian Calendar. Show all posts
Showing posts with label Gregorian Calendar. Show all posts

4 October 2023

The Gregorian Calendar

Why a 16th century Pope decreed that 10 days would not happen

The cover page of the first printed edition of the calendar, in 1582
The cover page of the first printed
edition of the calendar, in 1582
The Gregorian Calendar, which is used today by every country in the world with just four exceptions, was introduced by Pope Gregory XIII on this day in 1582.

The calendar replaced the Julian calendar, which had been implemented by Julius Caesar in 46 BC but which was based on a miscalculation of the length of the solar year and had gradually fallen out of sync with the seasons.

The Catholic Church wanted to make the change because the actual spring equinox - one of the two days in each year when the sun appears directly above the equator - was drifting further away from the ecclesiastical date of the equinox, which in turn determines the date of Easter. 

In Christian tradition, Easter marks the resurrection of Jesus three days after his crucifixion, which historical evidence suggests occurred around the time of the spring equinox, nominally dated as March 21. 

The miscalculation in the Julian calendar seems tiny, an assumption that the average solar year was exactly 365.25 days when the reality is 365.2422 days. Yet even after the inclusion of the supposedly corrective leap year every four years, the error meant that over the 1,628 years of the calendar’s use, the gap between the actual equinox and the date of the equinox in the ecclesiastical year had grown to 12.7 days.

Aloysus Lilius, one of a number of Italian scientists invited by Pope Gregory XIII to submit proposals for how the calendar might be reformed, realised that the addition of a leap year on an unvarying four-year cycle still made the calendar slightly too long. 

Lilius - sometimes called Luigi Lilio or Luigi Giglio - came up with a variation that adds leap days in years divisible by four, unless the year is also divisible by 100. If the year is also divisible by 400, a leap day is added regardless. 

A bust of the scientist Aloysus Lilius
A bust of the scientist
Aloysus Lilius
The German mathematician, Christopher Clavius, described as the architect of the Gregorian calendar, made slight modifications but largely adopted the Lilius formula as presented.

The formula did not completely correct the problem, but reduced the drifting apart of the solar equinox and the ecclesiastical equinox to just a few seconds per year, which means it will take until 4909 for the solar year and the Gregorian calendar year to be just one day out of sync. 

The more dramatic part of the change came in correcting the cumulative effect of the Julian calendar’s miscalculation so that re-alignment could happen immediately. To make this happen, 1582 was shortened by 10 days.

Thus when midnight was reached on Thursday, October 4, the date of the next day was changed to Friday, October 15.

The Gregorian calendar also renumbered the leap day as February 29, ending the practice in the Julian Calendar by which every four years February 24 lasted 48 hours rather than 24.

Nowadays, only four countries in the world - Afghanistan, Iran, Ethiopia and Nepal - do not use the Gregorian calendar, although its acceptance when first introduced was by no means universal and it was several hundred years before it became recognised as the world’s calendar.

Pope Gregory XIII had a reputation as a reformer
Pope Gregory XIII had a
reputation as a reformer
The countries and colonies of Spain, Portugal, France, the Polish-Lithuanian Commonwealth, Italy, the Catholic Low Countries and Luxembourg instituted it immediately.

However, the Protestant countries largely rejected the change at first because of its introduction by a Catholic pontiff. It was not until 1700 that Protestant Germany switched over, while Great Britain and its colonies - including at that time much of what would become the United States of America - remained faithful to the Julian calendar until 1752.

Another 121 years had passed before Japan made the change in 1873, China did not come on board until 1912 and Saudi Arabia - the last country to make the switch - not until just seven years ago, in 2016.

Many countries - including most of Western Europe - also agreed to standardise New Year’s Day as January 1 with the introduction of the Gregorian calendar. Until 1752, the start of a new year in Great Britain had been March 25 - the Feast of the Annunciation, also known as Lady Day.

The Piazza Maggiore, pictured at dusk, is the heart of the city of Bologna
The Piazza Maggiore, pictured at dusk, is the
heart of the city of Bologna
Travel tip:

Pope Gregory XIII was born Ugo Boncompagni in Bologna in 1502. Bologna is one of Italy's oldest cities, with a history that can be traced back to 1,000BC or possibly earlier, with a settlement that was developed into an urban area by the Etruscans, the Celts and the Romans.  The University of Bologna, the oldest in the world, was founded in 1088.  Bologna's city centre, which has undergone substantial restoration since the 1970s, is one of the largest and best preserved historical centres in Italy, characterised by 38km (24 miles) of walkways protected by porticoes.  At the heart of the city is the beautiful Piazza Maggiore, dominated by the Gothic Basilica of San Petronio, which at 132m long, 66m wide and with a facade that touches 51m at its tallest, is the 10th largest church in the world and the largest built in brick.

The rugged hill-top town of Cirò in Calabria. the birthplace of Aloysius Lilius
The rugged hill-top town of Cirò in Calabria.
the birthplace of Aloysius Lilius
Travel tip:

Aloysius Lilius, a doctor, astronomer, philosopher and chronologist, was born in Cirò, in Calabria, a rugged hill town about 40km (25 miles) north of the port city of Crotone, on the Ionian Sea coast, of which it offers commanding views. The site of a settlement since the Bronze Age, the town became an important regional centre between about 1300 and 1500, with a castle that has now fallen into disrepair. The town’s economy is based on agriculture, with the production of oil, wine, cereals and citruses as well as cattle breeding. Cirò is famous for the production of Calabria's most important wine, marketed simply as Cirò, a red wine made from Gaglioppo grapes, sometimes described as ‘Calabria’s Barolo’. On the coast below, Cirò Marina is a town of 14,000 inhabitants that has become a popular resort which has been awarded Blue Flag status for the quality of its sea water. Archaeological finds unearthed locally provide evidence of the area’s importance at the time of Magna Graecia.

Also on this day:

1633: The birth of physician Bernardino Ramazzini

1657: The birth of painter Francesco Solimena 

1720: The birth of printmaker Giovanni Battista Piranesi

1994: The birth of tenor Ignazio Boschetto

The Feast Day of Saint Francis of Assisi 


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7 January 2020

Pope Gregory XIII

Pontiff used his power to change the date overnight


Pope Gregory XIII took his papal name in honour of another reformer, Gregory I
Pope Gregory XIII took his papal name in
honour of another reformer, Gregory I
Pope Gregory XIII was born Ugo Boncompagni on this day in 1502 in Bologna.

Gregory XIII is chiefly remembered for bringing in the Gregorian calendar, which is still the internationally accepted calendar today.

As Ugo Boncompagni, he studied law in Bologna and graduated in 1530. He later taught jurisprudence and among his students were the Cardinals Alessandro Farnese and Carlo Borromeo.

Before he took holy orders, Ugo had an affair with Maddalena Fulchini, who gave birth to his illegitimate son, Giacomo Boncompagni.

Pope Paul III summoned Ugo to Rome in 1538 to work for him in a judicial capacity. He went on to work for Pope Paul IV and Pope Pius IV. Ugo was made Cardinal Priest of San Sisto Vecchio and sent to the Council of Trent by Pius IV.

He was also sent to be legate to Phillip II of Spain and formed a close relationship with the Spanish King.

In 1572, after the death of Pope Pius V, the 70-year-old Cardinal Boncompagni was chosen to be the next pope and assumed the name of Gregory XIII, in homage to Pope Gregory I, who is remembered as a great church reformer.

Mathematician and astronomer Christopher Clavius was co-writer of the calendar
Mathematician and astronomer Christopher
Clavius was co-writer of the calendar
Following in his namesake’s footsteps, Gregory XIII dedicated himself to reforming the Catholic Church and putting into practice the recommendations of the Council of Trent.

The Roman College of the Jesuits grew under his direction and became an important centre of learning. It is now known as the Pontifical Gregorian University.

Gregory XIII is best known for replacing the Julian calendar, which had been in use since 45 BC, with the calendar produced by astronomer Luigi Giglio and the German Jesuit priest, mathematician and astronomer Christopher Clavius, making the year slightly shorter.

In the Julian calendar, each year was too long, meaning that the March equinox had slipped back to an earlier date over the centuries.

The Pope decreed in 1582 that the day after Thursday, 4 October would be Friday, 15 October. The new calendar became known as the Gregorian calendar and is now used universally.

Gregory XIII encouraged Phillip II of Spain in his plans to dethrone Elizabeth I of England, causing English Protestants to regard all Catholics as potential traitors.

Detail of the monument to Pope Gregory VIII in the Basilica of St Peter in Rome
Detail of the monument to Pope Gregory VIII in the
Basilica of St Peter in Rome
He equipped an expedition to Ireland to help the Catholics in their struggle with the Protestants, but all the soldiers, sailors and women and children on board the boat were either beheaded or hanged on landing in Kerry, during what became known as the Smerwick Massacre.

In Rome, Gregory XIII had work completed on the magnificent Gregorian Chapel in the Basilica of Saint Peter and extended the Quirinale palace. He appointed his illegitimate son, Giacomo, as Castellan of Sant’Angelo and Gonfalonier of the Church. Venice enrolled Giacomo among its nobles and Phillip II made him one of his army generals. Gregory also helped his son acquire the Duchy of Sora on the border between the Papal States and the Kingdom of Naples.

To fund these projects, Gregory XIII confiscated houses and properties belonging to the church.

Pope Gregory XIII became ill with a fever in 1585 and died on 10 April, aged 83. He was succeeded by Pope Sixtus V, who found the papacy had been left considerably impoverished.


The campanile of the Basilica of San Sisto Vecchia, where Gregory XIII was priest
The campanile of the Basilica of San Sisto
Vecchia, where Gregory XIII was priest
Travel tip:

The Basilica of San Sisto Vecchia in Piazzale Numa Pompilo in Rome, where Pope Gregory XIII was Cardinal Priest for seven years, is one of 60 minor basilicas in the city. The basilica was built near the Baths of Caracalla in the fourth century and is dedicated to Pope Sixtus II, who was martyred in 258. His relics were transferred to the church from the Catacomb of Callixtus in the sixth century. San Sisto was rebuilt in the 13th century and restored in the 18th century, preserving only the bell tower, apse and a 13th century fresco cycle from the medieval church.

The dome of the Gregorian Chapel, finished by Giacomo della Porta, in St Peter's Basilica
The dome of the Gregorian Chapel, finished by Giacomo
della Porta, in St Peter's Basilica
Travel tip:

Pope Gregory XIII commissioned the architect Giacomo della Porta to complete the work started by Michelangelo on the chapel in St Peter’s Basilica that was to be named after the pontiff. It has been described as ‘the most beautiful chapel in the world’ because of its marbles, mother-of-pearl, precious stones, gilded bronze, multi-coloured mosaics and stucco ornamentation. The monument to Pope Gregory XIII in white marble, executed by Milanese sculptor Camillo Rusconi, is in the Basilica near the entrance to the Gregorian Chapel. The Pope is portrayed giving his blessing on top of an urn bearing a relief showing the promulgation of the Gregorian calendar in 1852.

Also on this day:

1625: The death of religious composer Ruggiero Giovanelli

1655: The death of Pope Innocent X

1797: The tricolore flag is hoisted for the first time

1920: The birth of actor Vincent Gardenia


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