The Ten Days That Didn't Exist

There are ten days that don't exist in history. Understanding why leads to a fascinating look at the nature of time—and one of the wildest conspiracy theories you've never heard of.

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Happy New Year!

For many of us, this is a time for resolutions, and new beginnings. We follow an annual tradition that comes in cycles following our planet’s orbit around the sun. Our lives are directed to an enormous degree by our relationship with time. But if you stop to think about it, the passage of time is an incredibly weird phenomenon.

For example, your head is slightly older than your feet.

This is due to an experimentally verified phenomenon known as “time dilation,” in which the gravity of a mass, such as the Earth, warps time, making time move slower closer to the mass. In human time scales on Earth, these are basically meaningless variations, utterly tiny fractions of a second over the course of a person’s lifetime. But this phenomenon, which was originally proposed by Einstein, and later confirmed using unbelievably precise atomic clocks, leads to a stunning conclusion: there is no such thing as objective time.

You don’t have to study modern physics to understand that humans have a constructed relationship with time. The names of our days of the week, for example, are holdovers from Norse/Anglo-Saxon times. Tuesday comes from Tiw, the god of war; Wednesday from Wodin, the god who was said to rule Valhalla; Thursday for Thor; and Friday for Frigge, the goddess of love. We insert our cultures, our histories, and our scientific progress into our concepts of time.

In this edition, I’m going to make sense of some really strange mysteries, which have too often been overlooked as we script our lives by calendars without stopping to consider where they came from or why we divide time as we do.

Let’s start with this: if you ever want to win a bet, challenge someone to identify a historical event—any event, of any kind, no matter how minor—that happened in, say, France, Italy, Spain, or Portugal, between October 5th, 1582 and October 14th of that same year. You will never lose that bet.

Or, perhaps you can ask someone how it’s possible that William III (the future king of England) set sail for England from the Netherlands and managed to arrive six days before he left, a rather impressive feat.

You might also wonder why, for about four hundred years in recorded history, there were two February 24ths that year—a day that just repeated, Groundhog Day-style.

For the literary fiends amongst you, you might know that Shakespeare and Cervantes died on the same date: April 23, 1616. That’s a stunning coincidence, of course, but what’s even more stunning is that even though those dates are correct, when Shakespeare died, Cervantes had already been dead for ten days.

Finally, there’s the wildest conspiracy theory you’ve never heard of. It’s a claim so brazen, so astonishingly broad, that it’s hard to grapple with its implications. It has its fair share of disciples, true believers who argue that historians are complicit in covering up the most astonishing heist of time ever perpetrated. Are they right?

The Roman Calendar

Our story starts, as so many do, with ancient Rome. In the earliest days of Rome, time was divided into ten monthly slices that followed the cycles of the moon (the moon is the linguistic root of the word month). Cumulatively, these ten slices added up to just 304 days, which as you may know, is far too short for one trip around the sun. To make up for the rest of the time, they would just slap on some extra winter time, which varied in length, to try to make everything line up properly with the seasons and the equinoxes and so on.

But it was a mess, so around 700 BCE, the legendary Roman King Numa Pompilius (who may or may not have existed) tacked on two additional months. This helped in the sense that the year was closer to the right length, but created naming problems that linger to today. For example, you may have noticed that September (which means seven, as in the French “sept”) or October (which means eight), or November (which means nine), and December (which means ten) are, respectively, the ninth, tenth, eleventh, and twelfth months of the year. They’re out of sync with their names.

However, there was still a lot of uncertainty about the calendar because the new version of the Roman calendar extended to 355 days, which still wasn’t quite long enough. Years needed to be adjusted, which created a jurisdiction of time control that was ripe for abuse. In fact, during the early Roman republic, religious leaders known as the pontifices had sole control of whether to lengthen or shorten years to try to make appropriate adjustments with the seasons. But like many powerful people throughout history, when given a bit of leeway, they sometimes abused it for their own benefit, lengthening the years when their political allies were in power and shortening them whenever their political adversaries were in charge.

For ordinary people, this uncertainty also created problems, because nobody really knew what the date was, which led this period to be known as the “years of confusion.”

The Longest Year

This temporal chaos persisted until 46 BC when Julius Caesar implemented the Julian Calendar. It had long been known that the solar year was about 365 and ¼ days long. The Julian Calendar was an attempt to make the human calendar align closely with the actual solar year. To achieve that, two changes needed to be made. First, the calendar needed to have 365 days plus an extra day every four years. Second, because the old ways of timekeeping had gotten so out of whack, Caesar needed to add quite a lot of days to one year.

If you thought 2020 felt long, keep this in mind: 46 BC was 445 days long.

There has long been a belief in human philosophy that the divine produces perfection, an ordered existence that shows off its godliness through its pristine elegance. As a result, it may have struck people that it was odd that a year was 365.25 days long rather than just 365 exactly. But at least that year length could easily be sorted out by just tacking on an extra day every four years and the problem would be solved.

Starting around 46 BC, these early leap years were included by doubling February 24th—just having it happen twice, back-to-back, rather than adding a February 29th as we do now.

There was still a problem, however. Earth’s orbit around the sun is even less pristine than the ancients might have hoped. It turns out a year actually takes 365.24219 days. Now, admittedly there’s not much of a difference between 365.25 and 365.24219. Over the course of a year, however, this divergence meant that the Julian calendar would be thrown off by eleven minutes and fourteen seconds. Not massive, but not zero, either.

Calendars needed to be precise for two main reasons. The first was related to knowing when the equinoxes would fall, for agricultural reasons. The second reason was religious, and took on particular significance after the Council of Nicea in 325 AD, in which the dates of major religious holidays (and especially Easter) were standardized. It would be a scandal to celebrate Easter on the “wrong” date. (Some Christians also worried that their prayers would be ineffective if sent to God at the incorrect time).

Over the centuries, the eleven minutes and fourteen seconds started to add up. Every 128 years, the Julian calendar would become one day out of sync with the “true” year, even with the leap year adjustments. By the 16th century, it was starting to become a glaring problem. Religious scholars calculated that Easter had drifted by ten days from where it should have been according to the system established twelve centuries earlier in the Council of Nicea.  

The Pope Who Made Ten Days Disappear

In the sixteenth century, Pope Gregory XIII decided to fix the problem, permanently. He sought advice from sages—and was particularly swayed by the suggestions of a physician named Aloysius Lilius (often known as Lilio). Lilio convinced the Pope that his calculations showed that the calendar needed to have 97 leap years every 400 years, rather than 100 every 400.

To achieve that, a simple proposal was made: there would be no leap years on any year that was neatly divisible by 100, unless that year was also divisible by 400. That’s why there was a February 29th in the year 2000, but not in 1900.

With that simple adjustment, Gregory XIII could be the man who ensured that Easter was always celebrated at the right time.

Lilio argued that the adjustment could be made gradually, slowly bringing 16th century Christian dates into sync with the Council of Nicea’s prescription for when Easter should be, but Gregory XIII listened instead to the German mathematician Christopher Clavius, who suggested that the reform be done in one fell swoop.

Ten days would have to be abruptly deleted from history.

By Papal decree, the Gregorian calendar came into existence in 1582. According to Christian doctrine and the new calendar, if you went to sleep on October 4th, 1582, you woke up on October 15th. The ten intervening days simply didn’t exist.

Countries that had close links to the Catholic Church, such as Spain, France, Portugal, the Polish commonwealth Italy, etc, quickly shifted calendars. But because the Protestant Reformation was already well underway elsewhere, other countries resisted.

It became a major political issue in England, which had only recently split from Rome, driven by Henry VIII’s desire for a divorce. To capitulate timekeeping to a calendar implemented by the Pope would be, in the eyes of some, an acknowledgement of his authority. Other countries thought this was a slippery slope, a Trojan horse that would start with calendars, and end with the Catholic Church again asserting its control over most of Europe.

As a result, England (later the United Kingdom) didn’t adopt the Gregorian calendar until 1752 (America, as a colony, made the switch at the same time—it has created uncertainty over when George Washington’s birthday was).

Britain’s late adoption of the calendar meant that traveling between some parts of Europe and others was a bit like traveling back in time, such that William III set sail from the Netherlands on November 11, 1688 but arrived in England on November 5th. This is also the reason why Shakespeare and Cervantes are said to have died on the same date, even though they actually died ten days apart.

Incidentally, this is also the reason why I, and everyone else in the UK, pays taxes according to a tax year that runs until April 5th. The New Year in England used to start on March 25th, which was known as Lady Day, the date when the archangel Gabriel was said to have informed Mary that she would be the mother of Jesus Christ. That was New Year’s Day from 1155 until 1752, when the Gregorian Calendar was adopted. When the eleven day shift was made, March 25th became April 5th, and the tax year still reflects this historical shift (it had to be eleven days rather than ten because it was more than 128 years after 1582).

For hundreds of years, many European countries used different calendars. Greece, for example, didn’t make the shift until 1923. This led to many documents being printed with two dates, one Julian, one Gregorian.

Now, the Gregorian calendar is pretty good, but it’s not perfect. If humans make it thousands of years into the future, we’ll eventually need to make an adjustment. The calendar will be off by about one day after roughly 7,700 years.  

Moreover, the day that we call the “summer solstice” isn’t always exactly right. Every so often, the solstice is closer to June 23rd, while by the end of this century, it’ll briefly be closer to June 20th.

Did the Early Middle Ages Exist?

Now, here is where we get to one of the wildest conspiracy theories I’ve ever heard of, which is called the Phantom Time Hypothesis.

Its central claim is this: the early Middle Ages didn’t exist.

Specifically, three centuries—from roughly 614 to 911 AD—never happened. But to make us think they did, there’s been a wilful ignorance at best, or a cover-up at worst, amongst historians to make us think that those fake centuries are real.

This sounds ridiculous, but the people who suggested it aren’t your run-of-the-mill crackpot crazies. It was advanced in a paper by the publisher, writer, and historical revisionist Heribert Illig. Illig got a lot of attention for the theory in the early 1990s, and some historical journals even devoted issues to discussing his proposal.

Illig’s claims boiled down to this: there doesn’t seem to be a lot of reliable archaeological evidence from this period; written sources with dates are inconclusive because people way back then might have been confused about which year it was; and, crucially, that the Gregorian reform of deleting ten days is proof that three centuries couldn’t have existed.

It’s this last claim that warrants our attention, because Illig was right, at least in one way. As I told you above, the Julian calendar would get out-of-sync one day for roughly every 128 years. By 1582, the Julian calendar had been in place for more than 1,600 years. By October 1582, then, to fix things, Pope Gregory XIII would have needed to delete 12.7 days, not ten.

As one of the proponents of the Phantom Time Hypothesis, Dr. Hans-Ulrich Niemitz, writes:

Now please calculate: how many Julian years does it take to produce an error of 10 days? The answer is 1257 years. The question – at which date was the Julian calendar correct – can be calculated with the following amazing result: 1582 minus 1257 = 325… It seems, unbelievably, that Caesar introduced his calendar in 325 AD. This is unbelievable because by then he had already been dead for more than 300 years. If 16 centuries had passed since Caesar’s introduction of his calendar, the Julian calendar in Gregory’s time would have been out of sync with the astronomical situation by 13 days, not 10.

Astonishingly, it appears these conspiracy theorists – who gained a lot of traction and still have a decent following – failed to notice the significance of the date 325. That was the year of the Council of Nicea, in which the dates of Easter and other Christian holidays were standardized. Gregory XIII wasn’t trying to align his calendar with Julius Caesar but rather with Easter, as decreed in 325 AD.

So, it all makes perfect sense. No crazy conspiracy theory is necessary.

(If you’re interested in a lengthier debunking of this ridiculous theory, complete with evidence from carbon dating and convincing evidence from tree rings, I recommend this excellent post from The Public Medievalist or this one from The Skeptoid).

What fascinates me about this realm of knowledge, however, mostly isn’t the crackpot conspiracies. Instead, it’s the notion that time is, to a greater extent than we acknowledge, a human construction. For most of human history, the ways that we divided our calendars didn’t actually align with our planet’s orbits around the sun. Weeks are arbitrary divisions of time. Months are arbitrarily chosen, each with varying lengths. We live our lives and get paid according to moon cycles, which is a human choice, not something pre-ordained.

So, this is quite a lengthy way to say: Happy New Year!

That is…unless you still follow the Julian calendar, in which case it’s not for a few days still, or if you still stick to the old celebration of Lady Day, in which case you can celebrate in a few months when the British tax year comes to an end.

Thanks very much for being a paid subscriber to The Garden of Forking Paths. I really appreciate it. I hope to hear your thoughts in the comments below. And please share this article and tell your friends about the newsletter, if you feel so inclined.

If you’re interested in reading more about time and the contested history of math and timekeeping around Pope Gregory XIII’s intervention, I highly recommend the book Infinitesimal by Amir Alexander. For a more general introduction to the mind-bending physics of time, I strongly recommend The Order of Time by Carlo Rovelli.