by The Gregorian Calendar was introduced in 1582, shifting the dates of the New Year and Easter, and removing 11 days from October. How controversial was it?
The Gregorian Calendar is the one most countries use today. It contains all the elements we are familiar with: years of 12 months and 365 days, starting each time on January 1.
The 365 day length is set by the Earth’s rotation around the sun; this is roughly how long it takes us to complete one trip.
The Gregorian Calendar was born out of its predecessor, the Julian Calendar. Named after Julius Caesar, who oversaw its implementation, the two calendars are very similar.
The Julian Calendar was used for 1500 years, and largely worked well. But there was one crucial flaw in its design, that eventually led to its replacement.
Caesar was a Roman general who seized control of the Roman Republic, turning it into an Empire, in 49 BCE. At the time, the Romans held sway across much of Europe, their territory stretching from Gaul (present day France) to Syria.
Later it would expand even further.
The Roman calendar at the time was ‘lunisolar’, based on the moon’s rotation around the earth. While the cycles of the moon were a useful measure of time in small increments, especially for an agricultural society, over longer periods this system had a weakness.
The moon takes 29.5 days to complete a rotation around the earth; 12 of these are completed in a year, giving an annual length to the calendar of 355 days. But based on astronomical observations, it was already known that a year was 365 days long.
This discrepancy slowly pushed the calendar out of sync with the seasons. An ‘intercalary month’ of a few day’s duration would be added to the end of the year, to realign the calendar with reality.
Caesar was reform minded, and determined to implement a new system to correct this issue permanently.
Caesar took advice from the Alexandrian astronomer Sosigenes, and in 46 BCE introduced a new solar-based calendar modelled on the Egyptian system. This ‘Julian Calendar’ fixed the length of the year at 365 days, with the existing months adjusted to fit this timeframe.
Astronomers knew that the solar year was about a quarter day longer than 365, so an extra day was added every four years to account for the fraction. This ‘Leap Day’ was added to February as this was then the final month of the year; New Year’s Day was celebrated in March.
The Julian Calendar had a 12-month structure as this was already entrenched in Roman society.
Rather than reinventing the entire framework, the new calendar standardised what already existed, making it easier to adjust to. Caesar’s personal power, and the reach of his Empire, meant the new system could be implemented across Europe relatively quickly.
Caesar lived before the time of Jesus, so did not have to consider significant Christian dates when designing his calendar. Christianity did not become the dominant religion in Europe until the 4th century CE, boosted considerably by the conversion of the Roman Emperor Constantine.
One of the most important dates in the Christian calendar is Easter.
Commemorating the death, and resurrection, of Christ, Easter is somewhat difficult to determine. The Bible stated that Jesus’ resurrection occurred on the third day after the Jewish holiday of Passover, this then set the date for his death as well.
The problem is that Passover is celebrated on a different date each year. This led to different Christian sects celebrating Easter at different times.
To settle the dispute, in 325 CE the Council of Nicea decreed that Easter would be observed on the first Sunday following the first full moon after the spring equinox (read my article about the origins of Easter, here).
This seemed to solve the problem.
The astronomers in Julius Caesar’s era had done a remarkable job of calculating the solar year. However, their figure of 365.25 days was not entirely accurate.
The actual solar year (sometimes called a ‘tropical year‘) is 365.2422 days, a difference of about 11 minutes per year. While minor, over a long enough period this small variance would gradually push the calendar out of sync with the seasons again.
The impact on Christianity was the placement of the spring equinox. As the calendar moved out of alignment with the seasons, the date of the equinox changed, which then shifted the placement of Easter.
The problem grew steadily worse over time.
By the later 16th century, the formal calendar was 10 days out of alignment with the solar year. In 1582, Pope Gregory XIII decided to act.
Gregory commissioned a study of the problem, the key analysis would come from Italian astronomer Aloysius Lilius, and Jesuit mathematician Christopher Clavius. They proposed a subtle but decisive adjustment.
Leap years would still occur every four years, century years (1600, 1700, 1800 etc) would only be leap years if divisible by 400. So for example, 1600 and 2000 would be leap years, 1700, 1800 and 1900 would not.
This was enough to correct for the 11 minute annual shortfall.
While the new system was settled upon, this left the problem of the 10 days the Julian Calendar had drifted out of alignment. To correct this, days were simply removed from the calendar: Thursday, October 4, 1582, was followed immediately by Friday, October 15.
One more change was bundled into the reforms.
The Julian Calendar had moved New Years Day to January 1. But after the fall of the Roman Empire, European Christians had returned to celebrating it either on December 25, or March 25, at the Feast of Annunciation.
Gregory wished to keep December 25 as a celebration of Christ’s birth, and his advisor’s felt March was too late in the year. So New Year’s Day was officially moved back to January 1.
The revised ‘Gregorian Calendar’ was enacted in 1582 through the papal bull ‘Inter gravissimas’. The pope had authority over Catholic countries, these adopted the change straightaway.
Spain, Portugal, the Italian states, and parts of Poland and France had switched to the new calendar by the end of the year.
Non Catholic countries were resistant. The change was significant, both Protestant and and Orthodox rulers were reluctant to abandon the system they were used to; there was also great suspicion at the notion of the vanished 10 days.
And so for several centuries, different parts of Europe used different calendars.
Gradually the advantages of the new system began to tell, and more countries would adopt the Gregorian standard. Protestant German states changed in 1700, Britain and its colonies, including the United States, waited until 1752.
There are stories that protests broke out when the calendar was changed in some areas, including accounts of rioting, and angry mobs demanding their days back. The change was particularly controversial in England.
‘When the British government decided to alter the calendar and skip 11 days, many people mistakenly believed that their lives would be shortened by 11 days. They were also unhappy at the moving of saint’s days and holy days, and some objected to the imposition of what they saw as a ‘popish’ calendar.’
– ‘Give Us Our Eleven Days’, historic-uk.com
While there was some resistance, and definitely confusion, claims of ‘calendar riots’ appear to be exaggerated. And once the new calendar was in place, and nothing dramatic occurred, people were able to adjust.
In the Orthodox world, change did not come until the 20th century.
Russia switched only in 1918, and after the Bolshevik Revolution, meaning the ‘October Revolution’ actually took place in November. Greece changed in 1923, becoming the last European nation to do so.
Some Orthodox churches still follow the old calendar today. New Years Day in these communities is celebrated on January 14, reflecting the Julian Calendar and its 11 minute discrepancy, from 2 000 years ago.
