The year that lasted 445 days due to confusion in the calendar – 03/22/2024 – Science

There was a time when the calendar was very confusing. The harvest celebration festival, for example, fell in the middle of spring.

It was the 1st century BC According to rituals, there should be vegetables ready to eat during the festival. But the farmer only had to look at the field and it was clear that the harvest was still several months away.

The reason was the first Roman calendar. It became so unregulated that important annual festivals bore less and less resemblance to what happened in the real world. Until Julius Caesar (100 BC – 44 BC) wanted to correct this system that no longer made sense.

It was not an easy task. It was necessary to correct the calendar of the Roman Empire and adjust it to the rotation of the Earth on its axis (one day) and its orbit around the Sun (one year).

Caesar’s solution gave us the longest year in history. He added months to the calendar and then removed them, fixed the calendar to the seasons and created the leap year. It was a huge project, which almost went wrong due to a peculiarity of Roman mathematics.

We are in 46 BC, the year of confusion.

The year 46 BC may have been complicated, but not as complicated as the previous one, according to history professor Helen Parish, visiting from the University of Reading, in the United Kingdom.

The first Roman calendar was determined by the cycles of the Moon and the agricultural year. Looking at it with modern eyes, the impression is that something is missing.

The year had only ten months. It began in March (spring in the northern hemisphere) and the tenth month of the year — the last — was what we know today as December.

Six of these months had 30 days and four had 31. In total, the year had 304 days.

So what were the remaining days like?

“The two months of the year when there was no work to be done in the field were simply not counted,” explains Parish.

In other words, the Sun rose and set, but officially no day had passed on the first Roman calendar. “That’s when complications began to arise,” according to the teacher.

In 731 BC, the second king of Rome, Numa Pompilius (753 BC-673 BC), decided to improve the Roman calendar. He added additional months to cover the winter period.

“What is the purpose of a calendar that only covers part of the year?” asks Parish.

Pompílio’s response was to add 51 days to the calendar, creating the months we now call January and February. This extension increased the calendar year to 355 days. The number may seem strange, but it was chosen on purpose.

This number refers to the lunar year (12 lunar months), which is 354 days long. But, “due to Roman superstition with even numbers, one more day was added, totaling 355,” according to Parish.

In this reorganization, the months were arranged so that they all had odd numbers of days, except February (28).

“For this reason, February is considered bad luck and a time of social, cultural and political purification,” according to Parish. “It’s the time when you try to erase the past.”

For the teacher, Pompílio’s calendar was good progress, but there were still around 11 days left to reach the solar year of 365 days and a few hours.

“Even this improved Pompilius calendar still gets out of sync with the seasons very easily.”

Around the year 200 BC, the calendar was so far ahead that the Romans recorded a near-total solar eclipse observed in Rome on what would now be March 14 as having occurred on July 11th.

When the calendar reached this point of “such catastrophic error,” in Parish’s words, the emperor and Roman priests resorted to the timely insertion of an additional “intercalary” month, called a Mercedonian, to try to realign the calendar with the seasons.

But that didn’t work out very well. There was, for example, a tendency to add the Mercedonian when favored public authorities were in power and not to strictly align the calendar with the seasons.

The historian and classical writer Suetonius (69 AD 141 AD) complained that “long ago the negligence of the pontiffs had disordered much [o calendário]with his privilege of adding months or days at his own will, so that the harvest festivals did not fall in summer, nor the grape festivals in autumn”.

Which brings us back to Julius Caesar.

In the year 46 BC, the inclusion of a Mercedonian was already planned. But the astronomer Sosigenes of Alexandria, Caesar’s consultant, stated that the additional month would not be enough this time.

Following Sosigenes’ advice, Caesar added two more never-before-seen months to the year 46 BC — one with 33 and one with 34 days — to align the calendar with the Sun. These additions created the longest year in history, with 445 days, or 15 months.

After 46 BC, the Mercedonian, the two new months, and the practice of intercalary months as a whole were abandoned. If all went well, they would no longer be needed.

“So, we returned to a calendar more similar to what we recognize,” says Parish. “Excellent! This feels familiar and refreshing!”

But, unfortunately, aligning the calendar with the Sun is one thing — keeping it aligned is quite another. The drawback is that the number of days (Earth rotations) in a year (Earth orbits around the Sun) is not a round number.

“That’s where the whole problem starts,” explains astronomer Daniel Brown of Nottingham Trent University in the United Kingdom. The number of Earth rotations in one revolution of the planet around the Sun is about 365.2421897… days.

In other words, the Earth adds almost a quarter of an extra turn every time it completes an orbit around the Sun. Therefore, Sosigenes calculated that adding a day every four years — in February — would help compensate for the misalignment.

This system would have worked very well, at least for a while, if it weren’t for the idiosyncratic way in which the Romans counted years.

“They would look at the years and count: one, two, three, four,” explains Parish. “Then they would start again at four — so they would count: four, five, six, seven. Then they would start at seven — it would be seven, eight, nine, 10.”

“They accidentally counted one of those years twice. It didn’t take long to notice the start of the misalignment.”

This was corrected in the reign of Augustus. Leap years began to occur every four years instead of three and the Julian calendar began to work well.

“Julius Caesar is almost where the calendar needs to be,” says Parish.

New fixes

The Julian calendar could have been the definitive calendar if the Earth’s rotation did, in fact, complete exactly one quarter turn every year. But this difference is a little smaller, at about 11 minutes.

“In other words, we are slowly still becoming desynchronized,” according to Brown.

The solution only emerged much later, in 1582, when Pope Gregory 13 made further adjustments to the calendar.

“It was the correction made by the reform of the Gregorian calendar — observing this point and adapting the calendar a little more, taking care that [o ano bissexto] not just every four years, but to skip this rule every hundred years,” explains Brown.

“But then they noticed that it doesn’t match completely — the compensation is excessive. That’s why every 400 years you don’t skip the rule.”

This is why the year 2000, for example, was a leap year: because it is divisible by 100 and 400.

For Parish, “this all seems very organized,” but this is where politics begins to influence the course of time. “It is a calendar implemented by a papal bull and, in fact, has no value outside the Church and the tutelage of the bishop of Rome.”

There were people who complained that the pope actually stole 10 or 11 days of their time by adjusting the calendar, according to Parish. Still, over the centuries, more and more countries began to adopt the Gregorian calendar.

“But, gloriously, they didn’t adopt them all at once,” says Parish. “The calendar was fixed, but there were now calendars in different countries following very different models.”

These discrepancies mean that “you can have the most bizarre situation in which a reply written in England to a letter that arrived from Spain may appear to have been sent before the first one arrived,” explains Parish, “because England is ahead of the curve.” of Spain on the calendar.”

Since being widely adopted and synchronized internationally, the Gregorian calendar has offered a few millennia of precision. But he’s still not perfect.

In fact, in the mid-56th century, “someone will scratch their head and say, ‘Wait a minute, today is supposed to be Monday, but it actually feels like Tuesday,'” according to Parish. “I think that’s probably a margin of error that we’ll end up accepting.”

At least the Gregorian calendar saved us some time until Monday arrives. Or is it Tuesday?

_{Read the original version of this report (in English) on the BBC Future website}