The Ancients - How Julius Caesar Changed Time

Episode Date: December 30, 2021

We’re finishing off 2021 with what is perhaps Julius Caesar’s greatest legacy. It’s not a military victory or battle, but one of the many political reforms that truly has stood the test of time: the Julian calendar. Before, calendars were largely based on the lunar calendar, and believe it or not, were pretty flexible, and therefore easily manipulated for political gain. (Need more time to collect some taxes? Just add three more days!)In this episode, Tristan is joined by Dr Philip Nothaft to discuss how and why this reform came about, and the lasting impact of this watershed moment today.Thank you so much for listening to The Ancients this year, it’s been so fun to have you along for the chariot ride. We can’t wait to bring you even more exciting ancient history in 2022! If you can’t wait, why not subscribe to our Ancient History Thursday newsletter here. If you've enjoyed the podcast this year, why not leave a rating and review, we'd love to know what you think.If you'd like to learn even more, we also have hundreds of history documentaries, ad free podcasts and audiobooks at History Hit - subscribe today! To download, go to Android or Apple store.Music:Time Is Palpable - Bradley Andrew Segal & Dorian Charnis

Hi, I'm Tristan Hughes, and if you would like the Ancient ad-free, get early access and bonus episodes, sign up to History Hit. With a History Hit subscription, you can also watch hundreds of hours of original documentaries, including my recent documentary all about Petra and the Nabataeans, and enjoy a new release every week. Sign up now by visiting historyhit.com slash subscribe. It's The Ancients on History Hit. I'm Tristan Hughes, your host. And in today's podcast, well, it's the end of 2021. I think it's time to think about calendars.

We're going into 2022. You need your new calendar. You need your new diary already for the new year. And so in this podcast, we're going to be focusing more on time. We're going to be focusing in on how Julius Caesar changed time. One of his greatest legacies has nothing to do with military victories, with military conquests. It's to do with an action near the end of his life where he changed the calendar. He reformed the calendar of ancient Rome. He created the Julian calendar. Now to talk through how this all came about, why there was this reform to the calendar at the time of Julius

Caesar and its huge, important, remarkable legacy, I was delighted to get on the podcast Dr. Philip Nottaft. Now, Philip, he's done work in Oxford. He also works in Ireland at Trinity College, Dublin. He knows a lot about calendars, not just in ancient history, but also in medieval history. And this was a really enlightening chat, particularly for someone like myself, who until recently never really fully realised the huge encompassing legacy of the Julian calendar

and still how it influences people to this day. Philip, it was wonderful to have him on the podcast to talk about this huge topic for the end of 2021. I really do hope you enjoy. And finally, a small thing from me. It's the end of 2021, thank you to everyone who's been listening to the Ancients podcast over the past year, it has been so much fun and it's been so wonderful to see the genuine interest and the growth of this podcast explaining why ancient history really is the coolest type of history of all. But stay tuned. This is only the beginning. We've got some

huge plans for 2022. So don't go anywhere. Anyways, that's enough from me. Because without further ado, here's Philip to talk all about how Julius Caesar changed time. Philip, thank you so much for taking the time to come on the podcast today. Pleasure. Now, this is an amazing topic, the emergence of the Julian calendar, how Julius Caesar changed time, as it were. OK, I know it's not that straightforward, but it's a fun title. But can we say the creation of the Julian calendar during the time of Julius Caesar,

Philip, this feels like one of the watershed moments in the whole of Roman history. Yes, I mean, I think it's largely because it coincides with a number of other momentous developments, right, the end of the Roman Republic and the way being paved for the imperial period. And so if you look at it in context, it's of course just one of many political reforms that were carried out by Caesar during the three or four years of him being a dictator. But it's the one reform that has really stood the test of time, as it were, and is still in effect to a very large extent. Yeah, literally has stood the test of time. You're quite right there. Let's delve into the background first of all then. So Roman calendars before Caesar, what do we know during the Roman Republic? What do we know about these calendars?

Well, basically not very much. But one thing that we have to look at in order to really understand what's going on is the bigger picture of calendars in antiquity. If you look at not just the Mediterranean world, but also the near Middle East, East Asia, India, and in fact, many other territories besides, you can make a generalization to the effect that up until the year 500 BC, very roughly speaking, the vast majority of attested ancient calendars were lunar in character, and they were all quite similar in the way they operated. That's not too surprising in a way, because there's a sense in which the moon is humanity's oldest scheduling instrument, in the sense that you don't have to be a genius or an astronomer to notice the waxing and waning of the moon, to notice the fact that this is a cyclical phenomenon,

and you can use that cycle to measure or to gauge the passage of time. We have this expression in English of many moons ago. That, in a way, is an artifact of an ancient practice of counting the number of lunations between two events. And once you're there, you can also start to use particular moments within a lunation cycle, such as a full moon, to schedule meetings or religious rituals or the start of a military campaign. And the next step would be to actually count the number of days within a lunation and use

that as a framework for organizing a society and for organizing various practices. The ideal moment for starting that count of days will be the disappearance of the moon. Once every lunation, the moon disappears between one and three days. And you can either use the last visibility of the thin crescent of the moon or what's more common in antiquity, the first visibility after invisibility to mark the beginning of a month. And then you count forward 29 or 30 days, depending on how long it takes. And that will be the kernel of a proper lunar calendar. 12 iterations of a lunar month will give you a lunar year, which will align very roughly with the change of the seasons. But it doesn't take very long to realize that sometimes

you have to count 13 months to get back to a particular seasonal parameter, such as the beginning of spring, whatever it may be. So most ancient lunar calendars have this practice of occasionally intercalating or adding a 13th month. And the general sort of uniting characteristics of most ancient lunar calendars up until a particular point in time, middle of the first millennium BC, is that they're very ad hoc and not pre-planned and very flexible. That is, decisions as to whether to insert an extra month or the decision of how long a particular month is going to be is left up to the discretion of maybe a ruler or a magistrate, a political body, a priestly, college, or something of that nature. And it's impossible for an individual to really predict in advance how long a particular year is going to be.

And that is a general situation which also would have applied to Rome early on in the early republican period and even beyond that in the sort of mythical pre-republican period. And one artifact of their practice is the division of a month into calends, knowns and aides. The calends are always the first day of a particular month and are a reference point for counting other days, counting them backwards, as a matter of fact. The term calends derives from kalare, which in turn is a loan word from Greek. It essentially means to call together or to assemble and to summon. And probably this is a reflection of the fact that early on, the beginning of a month in Rome would have been announced at a monthly assembly by a magistrate or by a priest because it depended on the moon actually being cited and that being the basis for beginning

a new lunar month. And the Ides, for instance, would have coincided originally with a full moon. The Nones are simply the ninth day counted inclusively prior to the full moon. And so you have this lunar framework in the Roman calendar, which eventually is abandoned, or at least is slightly weakened and altered in various ways. So we can talk about that maybe in a minute. But the general idea is that the Roman calendar initially was no different from most other calendars that we have any evidence for, based in the sense that they were all lunar, all very flexible, ad hoc and subject to the arbitration of political and religious bodies. I'll tell you what, Philip, as a scholar of this and approaching this from the 21st century,

this idea of a flexible calendar is very, very unusual indeed. It's so interesting to think that these ancient societies, whether it was very early Republican Rome or before Republican Rome, they could change the length of a year, the length of the calendar, if they so wished. Yes, and initially there was a very good reason for this. This was the only viable method really to keep the calendar aligned with the astronomical phenomena, with the moon and the sun or with the seasonal cycle. Because if you try to have a pre-planned fixed calendar that is similarly accurate in astronomical terms and needs quite a bit of astronomical expertise, that creates certain complications.

And so having, as it were, an empirical calendar that's very ad hoc in the way it's adjusted is much easier. But of course, it also creates a leeway for political bodies to tinker with the calendar, to make changes out of convenience. There's, for instance, evidence that in ancient Greek polities, sometimes days were inserted simply for convenience. Maybe there's an important festival coming up and there's not enough time for a theatrical troupe to arrive. And so an extra three days are inserted to make some allowance for that. Months might be prolonged or years might be prolonged. So there's more time for deliberations, for the passing of laws, for ceremonies. So there's lots of evidence, especially in the

Greek world, where each polis has its own separate calendar, that calendars are being manipulated in that way on a very ad hoc basis. And the same is, of course, also true in Rome. But in the specific case of Rome, this type of tinkering caused a certain misalignment between the calendar and the seasons quite early on. And what the Romans also did, and that's rather unusual, at some point during the Roman Republican period, they altered the length of the month permanently. So in a normal lunar framework, a month will either be 29 or 30 days, depending on when exactly the crescent of the moon is sighted. But the Romans implement fixed length for these months of 31 days or 29 days, or in the case of February of 28 days.

Nobody really knows why. But for the most part, all the numbers in the Roman calendar start to be counted as uneven numbers, maybe for some religious reasons. And so they develop a calendar which is no longer even notionally attached to the moon. It just works according to its own scheme. At the same time, the intercalation, which is also rather odd because it consists in periods of 22 or 23 days, which are inserted on average every other year, that intercalation is still very much at the discretion of a pontifical college. of a pontifical college. And there's a lot of evidence,

especially towards the end of the Roman Republican period, that the priests are susceptible to political influence, to bribery, to other forms of pressure to either intercalate or not to intercalate. For various reasons, tax farmers had a vested interest in having more time at their disposal to actually collect taxes, or an intercalation was beneficial to them. Magistrates might have had an interest

in having a longer term in office so there's more time to pass legislation. Others such as Cicero, who at one point he is marooned, right, around 50 BC, 51 BC he's marooned, and Calicchia is a pro-consul and he very much hopes that there won't be an intercalation so he can get home earlier and he actually tries to get his friend Atticus to make his political influence felt in Rome to prevent an intercalation from happening.

So you can see how the calendar is under a lot of political pressure and can be influenced at very short notice. And also that creates a situation where even in February, when the intercalation is supposed to take place, most people have no idea whether it's actually going to happen or not. And that creates a lot of uncertainty, obviously. And the other issue which we can talk about is the fact that the Roman calendar is increasingly whacked out of alignment with the seasons at various points in its history. And is this one example of that, when that happens, Philip, at this time, the end of the

Roman Republic, that you do see this real disalignment with the seasons? Yes, already, like, for instance, at the beginning of the 2nd century BC, if you compare, for instance, eclipses of the moon, which we can date very reliably using our astronomical knowledge, you compare the recorded Roman date, you can see that at the beginning of the 2nd century BC, the month of July would have fallen in early spring. And that situation was corrected later on, but the same type of chasm had re-emerged in the 50s BC once again. And that's why as part of the Julian reform, 90 days had to be inserted into the calendar or 67 days, depending on how you count it. The point is that there was one

year in Roman history, which had 445 days in total, which is the year 46 BC. And that elongation of the year was all about restoring a traditional alignment between individual month and their seasonal context, because there are obviously certain religious feasts, which have some at least notional connection to the seasons, to the agricultural cycle, and to have a complete mismatch would have been perceived as a problem, at least by certain people. That's also interesting. And before we really delve into the detail of how these reforms come about and how they are processed, as it were, under Caesar, I would first like to, because I've got it here, I'd love to talk about a particular artefact from the late Republic just before Caesar, because it does seem to be really interesting. I'd never heard of it before, before doing some

research for this. And this, you probably know I'm going, the Fasti Antioces Maiores. Now, Philip, what is this? Yeah, so that's essentially a painted wall calendar from the very end of the Roman Republic, right? This is a calendar which existed, as it were, at the eve of the Julian reform. It would have been created roughly between the 80s and 50s BC. And it was discovered, I think, in 1915 at Anzio, the ancient city of Antium. It's now displayed in a museum in Rome. And of course, it's a very fragmentary archaeological artifact, but we can still use it to reconstruct what this calendar would have looked like quite reliably. And the comforting thing is that it gives us a picture of the Roman

calendar, which aligns pretty closely to what we know from written sources, right? It's reassuring to know the sources aren't completely fantastical. It does confirm that we have these 31 day-long months, four of them, and then the other month are 29 days in length, except for February, which is 28 days, and then has this slot in the middle where the intercalary days will be inserted every other year, roughly speaking. It's also a calendar which marks the difference between so-called Dies Fasti, which is allowed days for certain legal actions and for litigations in courts, and Dies Nefasti, which are so-called banned days. And also it marks the assembly days for political assembly. It contains a lot of information and it gives us a rough idea of what the Roman calendar was like in Cicero's time, essentially.

That's brilliant. So you have this archaeological evidence to, as you say, to back up, let's say, Cicero's comments, which you mentioned earlier. That's fascinating for ancient history to have the archaeological evidence, which is backing up the literary evidence as background. We're not even on Julius Caesar himself yet for the Julian reforms. It's like for your for your field, that must be brilliant. It is brilliant. I mean, there's certain questions which a wall calendar cannot answer, and that's particularly the nitty gritty of when and how to intercalate and how that intercalation practice changed over time. The intercalation practice in theory is, of course, all about maintaining an alignment between the calendar and the seasons. And since that

intercalation happens in an ad hoc way and is subject to political decisions, a wall calendar cannot give you an account of what exactly happened. But it gives you the basic structure of the calendar. Well, let's then go on to the Julian reform itself, the emergence of the Julian calendar. So from what you were saying earlier, Philip, is it primarily the need for this calendar at this time? Is it primarily, can we say, an agricultural reason that it's introduced? Well, I think Caesar himself had agriculture in mind. There's really a mixture of motivations here. We should probably point out that we have no documentation that would give us a reliable picture of what Caesar himself may have thought, right? Contemporary sources on the Julian reform

of the calendar are practically non-existent, right? We have to base ourselves on much later accounts. So it's a bit difficult to really get inside Caesar's head. I mean, first of all, there was this issue of the seasonal misalignment that in principle could have been solved by a very simple correction, and that could have left the basic structure of the Roman calendar intact. But of course, Caesar did something else. He introduced a new calendar. He changed the operating system, as it were, of the calendar from a quasi-lunar arrangement into a solar calendar based on an Egyptian model. If you look at sort of the motivations that might have been behind this major change in the Roman calendar, first of all, what he accomplishes is

to introduce a very fixed, a very regulated, a very predictable calendar, which essentially depoliticizes the intercalation, right? So the power to make changes on a whim is sort of taken away from the priests and from the Senate. He also creates a calendar because it's so predictable and so fixed and regular, is ideally suited to the administration of an increasingly vast Mediterranean empire. That might not have been on his mind, but it certainly explains why this calendar remains in place for so long throughout the rest of Roman history. And then finally, and this is something that Caesar was certainly interested in, he realized that with this new

solar calendar, which represented the actual length of a solar year, he could create the backbone for a so-called parapagma. Parapagma is a type of Greek almanac which correlates stellar phenomena, such as stellar phases, the visibility, and the rising and setting of constellations, with agricultural and meteorological events and phenomena. That's an ancient Greek practice to draw up these parapagmata. And Caesar realized that with his new calendar, he can use the actual calendar as the backbone for such a parapegma, because you can assign

all these agricultural and astronomical events to individual dates in the calendar. And so apart from promulgating a reform of the calendar, he also published an agricultural almanac, if you so will, a Caesarian parapagma, which has not survived, but we have secondhand quotations which give us some sense of what it actually contained. So yes, agriculture, in a sense, was on his mind, on his own mind, when he decreed that reform. Philippe, you mentioned astronomy, so I'm going to keep on that a moment. Does it therefore seem to be this influence of Greek astronomy on the creation of this calendar and particular figures such as Hipparchus? Yes, so there are really sort of two basic influences that account for the shape the Julian calendar effectively took. There is the Egyptian background. I mentioned

earlier how up until the year 500 BC, all those calendars are lunar. There's one very significant exception, and that's the Egyptian calendar, which already in the third millennium BC switched to this highly regular 365-day arrangement, where you simply have a year of 365 days, which never changes its length, and which always remains the same. We believe, most historians would argue, that the reason the Egyptians opted for this very unusual format is because of the very high degree of dependency of the Egyptian culture and economy and society on the annual flooding of the Nile, the whole Nile flooding cycle. In fact, this calendar year was divided into three seasons, as it were, which all were connected to the high tide and low tide of the Nile, so to speak. And the solar year of the Egyptians remained an anomaly for most of

ancient history. However, then around 500 BC, Egypt is annexed by the Achaemenid Persian Empire, and the Persians start to adopt a version of this Egyptian calendar. And of course, only one or two years before the Julian Reform, Caesar is in fact physically in Egypt as part of the civil war, reform. Caesar is in fact physically in Egypt as part of the civil war and he has an opportunity to take in some new influences from Egypt and one of these seems to have been an interest in the Egyptian calendar. At the same time of course we're now at this stage in history we're talking about a Greco-Egyptian culture specifically in Alexandria and there is of course a Greek astronomical tradition which pays particular attention to the length of the seasons and to the length of a so-called tropical year which in an ancient

context is the interval between two vernal equinoxes and it's really the Greek astronomers more so than other astronomical traditions who try to solve the question of how long is a year exactly and how long are the seasons exactly. And so by certainly the second century BC, you have some fairly precise knowledge to the effect that a tropical year is slightly shorter than 365 and a quarter days. In fact, already in 238 BC, the Ptolemaic ruler of Egypt at that time, Ptolemy III, tries to pass a decree, or at least he drafts a decree, which would have provided for the insertion of a leap day every fourth year, very similar to the later Julian calendar.

His goal at the time was to have a feast day in his honor remain connected or remain associated with a particular astronomical event, namely the annual heliacal rising of the star of Sirius. And in order to maintain that synchronism, this leap day would have been inserted based essentially on Greek astronomical knowledge. But that decree never took effect in Egypt. But it's possible that Caesar still knew about that precedent, or that his advisor, it's quite likely that he had scientific advisors who were originally based in Alexandria. We know of one named Sosigenes, a Greek astronomer who's quite plausibly from Alexandria,

and they may well have had some notion of this 3rd century BC precedent, as it were. But yes, in very simple terms, there is a confluence of Greek astronomy and Egyptian calendrical tradition, which account for the Julian calendar as it then became law. Let's go on to the Julian calendar then itself. And you mentioned how we don't have any contemporary literary Julian calendar as it then became law. Let's go on to the Julian calendar then itself and you mentioned how we don't have any like contemporary literary sources as it were but we do have a later source don't we one particular later source which gives us a lot of detail about sorry the precise steps involved in this reform what is this? Yes the most detailed

and verbose account is in the Saturnalia by Macrobius. Macrobius is, of course, himself a Roman magistrate of the beginning of the 5th century. I think he wrote that text roughly in the second quarter of the 5th century. And the Saturnalia is a very entertaining dialogue between a number of 4th century Roman aristocrats. And in one very lengthy section of that work, they discuss the whole history of time reckoning and especially calendrical reckoning, especially in Rome. What Macrobius does here is to combine various bits from a long-standing antiquarian tradition in Rome that goes back to the first century BC of Roman scholars trying to understand their own institutions. And of course, there's a lot of guesswork there and a lot of myth-making and etiological myths being sort of created to explain certain phenomena.

But there's also some reliable information there. And of course, when it comes to the Julian reform, that is sufficiently close to recorded history for us to be able to take most of what Macrobius says at face value. And so what are these steps, Philip? What are these steps, Philip? Well, first of all, as mentioned earlier, there was this requirement to somehow get the month of the Roman calendar back into alignment with the seasons. And for that purpose, Caesar decreed this unusual year of 445 days. The big change compared to the previous Republican calendar was the insertion of 10 new days, which were distributed across different months. So some months acquired two new days, others only one day. The precise way in which this was done was guided by the requirement to be as conservative as possible. There was an attempt on Caesar's part not

to interfere with feast days the way the feast days related to the way that the days were counted backwards from the calends, aes itinerants, not to interfere in the accustomed intervals between important feast days. So for religious reasons, basically, it was a very conservative approach to inserting extra days into the calendar. But essentially, the calendar was bumped up from 355 to 365 days per year. And then the other major component is this new leap year rule of inserting an extra day in February every fourth year. And does Caesar also leave his personal mark on it? I'm thinking with the renaming of a certain month. Well, subsequent to his death, the Senate passes a law to rename the month of Quintilis into Julius or July in his honor. And that is repeated then subsequent to the death of his nephew Augustus.

As a result of that, Sextilis becomes the month of August or Augustus. So that's the way he leaves his mark, of course, not by his own decree, but as a result of the honours bestowed upon him after his death. I didn't know that. I didn't know that. But it's so interesting, though, those facts you get. You've got Rome in the calendar of today with July and August, don't you? That is quite something. And something which I also find really interesting, Philip, is that perhaps one of the most famous dates of the new Julian calendar from ancient Roman times is the date of the man who oversaw the creation of this new calendar's assassination barely a year

after his creation of the Julian calendar. Yeah, yes, the infamous Ides of March, that is correct. And of course, you know, without his reform, that would have been a different date in history. Welcome to Gone Medieval, the podcast that will dust off and polish up some of the medieval period's most fascinating characters and stories. So this is a really kind of funny way where, you know, medieval people differ from us immensely because as far as they are concerned,

sexual desire and interest in sex is a feminine trait. It's a very difficult one, isn't it? I mean, I think that Henry I did not probably intend to be buried under a school, and he is one of the great kings of medieval history. We found that about 18% of our sample had evidence of bunions. So we think this change over time is directly related to the type of footwear that people were wearing. I'm Dr Kat Jarman. And I'm Matt Lewis. And on Gone Medieval, we'll tell you just why the so-called Dark Ages

really weren't that dark after all. Subscribe to Gone Medieval from History Hit, wherever you get your podcasts. And so following Caesar and following Augustus, you know, August and July and all of that, the calendar, it outlives Caesar, it outlives Augustus, and it becomes one of the longest lasting, shall we say, legacies of ancient Rome.

Absolutely, yes. In a sense, it has never disappeared. I mean, the calendar we use today is, for all intents and purposes, exactly the same with the exception of one small detail concerning the leap year rule. But otherwise, structurally, nothing has changed about the calendar at all. It still begins on the same day, on the 1st of January, the month have the same names, the same length,

right? We still use Caesar's calendar. And how influential is the Christian church, and the early Christian church in particular, in preserving this calendar throughout the centuries? I think the church was maybe not so important in preserving it. I think that's largely due to the persistence of the Roman Empire, which, depending on how you look at it, only ended in 1453 or 1806. But the church is absolutely instrumental in its diffusion beyond the accustomed or traditional borders of the Roman Empire. If you think of territories such as Ireland, right, Ireland adopts Christianity around 400 maybe in the 5th century. As a result of Christianization, they also adopt the Julian calendar. The same happens in other parts of the world. For instance, Ethiopia, which is Christianized in the 4th century, adopts the Alexandrian calendar, which is a localized Egyptian variant of the Julian calendar.

And so maybe to overgeneralize, you can say wherever Christianity goes throughout its long history of expansion, so does the Julian calendar as a result. That's so interesting. So during the time of, let's say, the late Roman Empire, were there several different localized Julian calendar versions from wherever you were based in the Roman Empire? That's right. I mean, the Julian reform of the calendar only takes immediate effect in Italy and in parts of the Western Roman Empire. immediate effect in Italy and in parts of the Western Roman Empire. And it takes a while, maybe until the end of the reign of Augustus, that more far-flung parts of the empire, such as the Levant and Arabia and Asia Minor, follow suit. And they often do so as an express way of showing the loyalty to the emperor. But what happens in these more far-flung eastern parts of the empire is that they create localized

versions. So they maintain the traditional beginning of the year. They tend to maintain their own names for the months. But they make sure that the year has 365 days and they make sure to intercalate one day every four years. So, for instance, the Alexandrian calendar, which I just mentioned, is for all intents and purposes, the old Egyptian calendar with an extra leap year inserted, right? Yeah. all intents and purposes the old egyptian calendar with an extra leap year inserted right but in a way it's synchronous with the julian calendar because once you know where the year begins relative to the julian calendar you can figure out the precise relation between these calendars without having to calculate a lot so in a sense they all go in lockstep from maybe the first century a.d onwards i see that that diffusion of the calendar, not just in the Roman Empire,

but also, as you mentioned earlier, outside the borders of the traditional Roman Empire and outlasting it. And let's go back to Ireland then for a bit, like the early medieval period, because I know you've done a lot of work around this. And it's really interesting because explain to me this early medieval Irish link

between the Julian calendar and its Roman roots going back to Caesar? Yeah, I think what makes the case of Ireland interesting is that Irish monks, who of course developed a very flourishing and very sophisticated learned culture subsequent to Christianisation, to them and to Irish audiences in general, the Julian calendar was a bit of a foreign object, compared to most of the rest of the Christian world, which had been influenced by the Roman Empire prior to the Christianization. Here you have a culture which learns Latin as a foreign language and also adopts certain elements of Roman culture as it were, as a foreign element.

And so that creates a need to explore what the Julian calendar is, the meaning of its individual months and various other structural issues. And so it's no accident, perhaps, that Ireland becomes the epicenter for the development of a new type of learned text or learned discipline, which becomes extremely influential in medieval Europe, which is known as the computus, which is a type of discipline or text, which is all about explaining the calendar, its astronomical underpinnings, its historical background, and then first and foremost, as its most important purpose, explaining how to calculate the dates of Easter and other mobile feast days. So in a sense, teaching the fundamentals of the Roman calendar is just a

preliminary step towards talking about the date of Easter. But still, for this reason, computistical texts transport a lot of historical knowledge and also etymological knowledge about the old Roman calendar and make sure that throughout medieval European history, pretty much every educated person would have known about the pagan background of the Roman calendar, would have known about Julius Caesar and his role in introducing that calendar. It all remained common knowledge and also fairly accurate knowledge thanks to this existence of the computus as a genre that transports knowledge on calendrical issues. I mean that's absolutely astonishing when you think let's say in the early Christian world Philip in various other ways there is an attempt to very much to deride the pagan Rome before them as this place of decadence this horrific place

compared to the great you know the good Christian world that comes after it. But as you were saying, for the legacy of the Julian calendar in this early medieval Irish period, there's a welcomeness almost to show that learning to emphasize the background of this calendar from where to... Whether you're in your running era, Pilates era or yoga era, dive into Peloton workouts that work with you. From meditating at your kid's game to mastering a strength program, they've got everything you need to keep knocking down your goals. No pressure to be who you're not. Just workouts and classes to strengthen who you are. So no matter your era, make it your best with Peloton.

Find your push. Find your power. Peloton. Visit Peloton at onepeloton.ca. Discuss it, to focus on it, to learn more about the calendar and how it can be, can we say, improved in several ways. Yeah, that is absolutely right. And of course, the Latin medieval Christian attitude towards especially Julius Caesar and Augustus tends to be relatively positive, right? Because they were seen as sort of historical agents which paved the way for the Roman Empire and for the spread of Christianity more generally. And Caesar has a relatively positive image in the Middle Ages, right? It's no accident that Dante places his assassins, Brutus and Longinus, in the

innermost depth of hell, right? Fair enough, fair enough indeed. And also I've got the figure, one of the most influential figures of early medieval history, correct me if I'm wrong on that, but the venerable Bede. He also seems to be influenced by this too. Yeah, so Bede picks up lots of cues and influences from this Irish computistical tradition

and he writes what effectively becomes the most influential calendar textbook of the entire Middle Ages, a work called the Temporum Ratione, which he wrote in 725. And that is sort of the classical computistical text, which has several chapters on the history of the Roman calendar. And a lot of the information that is common knowledge later on can be derived or can be traced back to this particular text. He wasn't the first writer in

this story, but certainly the most influential and widely read one. So is it fair to say, Philip, that between 500 and let's say 1000 AD, like this early medieval period, that the Julian calendar and learning about it, it was at the nucleus, it was a crux, it was at the centre of medieval learning? Yes, very much so. In the sense that, of course, the early medieval monastic curriculum was relatively limited, right? Most of the things that were taught at monastic schools were geared towards divine worship. And so the computus, the study of the calendar, was the one element or the one link in the chain where there was an actual opportunity and a leeway for studying astronomy and for studying areas of knowledge that fell outside the confines of divine worship. And that's why the competus was of paramount importance

before sort of the Western curriculum changes thanks to influences from the outside. And so, as you correctly say, it's especially between 500 and 1000 that the competus reigns supreme as a learned discipline that allows for the study of the natural world and for the study of astronomy. And the natural world, which leads into the next thing, which is this other Roman author, Pliny. He also seems to be really popular at this time too.

Yes, exactly. I mean, computistical authors in particular, of course, tried to read everything they can get their hands on that would elucidate the background, again, of the Roman calendar and also of astronomical phenomena more generally. And Pliny was simply one of those texts at hand already in the early Middle Ages that enjoyed a certain degree of circulation across western Europe already in the 8th and 9th century and Bede in particular makes heavy use of Pliny for precisely that reason. Now Philip with Pliny with the Julian calendar let's move on to this seems like one of the great confusions one of the great struggles of this period. And I've got the name here, the Vernal Equinox and trying to figure out this date in the calendar.

I know it's a huge topic. I know it's a huge question for me to ask. But talk us through why there is such confusion, why there is such debate over this early medieval period about trying to figure out when the date of Easter is. Yes, I mean, the basic problem with the date of Easter is that it's a mobile feast day, which means that its date relative to the Julian calendar changes each year. And that's an artifact of the Jewish background to Christianity. Easter is essentially the Christian version of Passover. Jesus died and resurrected at the time of Passover. And that's why these events are commemorated every year, notionally at the time of Passover. Jesus died and resurrected at the time of Passover, and that's why these events are commemorated every year notionally at the time of Passover. So Christians

from the beginning used a lunar calendar to pinpoint the right time to commemorate these events. At the beginning, they used simply the Jewish calendar, which was a lunar calendar like most ancient calendars, and as time went by, they created lunar cycles, which simply were there to identify the dates of the new moon in the Julian calendar, so they could find the appropriate time to celebrate Easter. The thing is that this is an arithmetically and astronomically relatively complex problem, which allows for a number of different solutions. And so during late antiquity, and also still in the early Middle Ages, you have a multiplicity of methods that are being used. And it takes a while until Christians have sort of sussed out and hashed out the correct way of going about celebrating Easter. And it takes a while until they're all on the same page.

So there's so-called Easter controversies in the early history of the church. But to cut a long story short, at some stage, a canonical way of celebrating Easter is established, which in ecclesiastical tradition is traced back to the Council of Nicaea of 325. That's actually slightly apocryphal, but it was widely believed that this is the council which established the canonical set of rules. And according to this canonical definition, Easter always has to be the first Sunday after the first full moon that falls on or after the spring equinox. And the spring equinox for ecclesiastical computistical purposes was always supposed to be the 21st of March.

And so in the ecclesiastical tradition, that's the date of the equinox. There's a bit of a confusion going on in this early period, partly because there are other methods of Easter reckoning and also because there's a longstanding Roman tradition of putting the equinox a bit later on the 25th of March. But for all intents and purposes, in an Easter reckoning context, it, on the 25th of March. But for all intents and purposes, in an Easter

reckoning context, it's always the 21st of March, which would have been the correct date roughly in the 3rd or 4th century. But of course, what's crucial is the fact that an actual equinox here, the interval between the two equinoxes, is about 11 minutes shorter than an average Julian year. And so over time, the date of the equinox starts to move, to shift towards the beginning of the year very gradually at a rate of roughly one day every 130 years. So there are two problems going on in the early Middle Ages. There's a slight confusion as to what the canonical tradition is supposed to be,

but more importantly, over time, as we approach the high Middle Ages, there's a growing awareness that, in fact, the equinox has moved away from its canonical, its legal date. And that, of course, is one of the nuclei from which a calendar reform debate starts to develop starting maybe in the 12th century. Yes, Philip, I mean, talk us through and let's go from, let's say, 1000 to 1200 at the moment, like that next been the high middle ages, like the Julian calendar at this time, the background that you've just laid out there, it sounds like it's paving the way for further scrutiny in this period. Yes, that's right.

I mean, this is a very drawn out and complex development, but a crucial set of changes that occurs in the high Middle Ages is the knowledge transfer from Arabic to Latin, which is, of course, a characteristic hallmark of the history of science in the 12th century. which is, of course, a characteristic hallmark of the history of science in the 12th century. And as a result of this knowledge transfer, new astronomical parameters became available in Latin Europe and also new astronomical theories. And all of a sudden, it was possible to really articulate in writing what the problem was, the fact that an actual solar year is a bit shorter than a Julian year. It was possible to articulate also the reason why the lunar cycle no longer properly aligned with the visible full and new moons. That was another error of the ecclesiastical calendar, which at least in theory meant that Easter was celebrated on the wrong date in many years. If

you take the astronomical criteria for Easter very seriously, the conclusion was inescapable that Easter was often celebrated on the wrong day. And so you have an error in the lunar calendar, you have an error in the solar calendar, you have an era in the solar calendar, and from the 12th century onwards, you also have the astronomical knowledge necessary to address the problem and to propose potential solutions, which eventually then leads to the Gregorian reform at the end of the 16th century.

Yes, Philip, I know it's a huge question. I know your main focus is this medieval period, but I will ask of it now, as the Joe blogs, as the general overview. I mean, how do we therefore get from, let's say, this period in like the 12th century to the 16th century, the late 16th century, and the ultimate official reform of the Julian calendar into what we now know today as the Gregorian calendar? Right, so there's a long period of around 400 years that is characterized by debates back and forth of how to implement a reform or whether it's practical to implement a reform. We have to bear in mind that the papacy doesn't always enjoy the same degree of influence and power in the context of Latin Christianity.

The question really is who actually has the authority to reform the calendar and And how far does this authority actually reach? And there are also practical problems. As I mentioned earlier, you have a calendar, which is really there for the celebration of Easter, right? If that Easter problem had not existed, Latin Christians could have been perfectly complacent about the fact that the equinox sort of drifts through the year. But because of the importance of Easter, they had to somehow address that problem, at least many people felt that way. And so you have two components, a lunar and a solar component, and they don't deteriorate exactly the same way. So to have a reformed calendar that would accurately track both the sun and the moon would have required a lot of complexity.

And the question is, how complex do you want your calendar to be so it's still intelligible to normal people or to the priests who have to operate with this calendar? That's one problem. The other problem is that it may be easy for the church to reform the method of Easter reckoning, but if that reform requires interventions in the civil calendar, which of course also governs the economy, it governs legal issues, it governs social life, then all of a sudden you have to interfere with the purview and the remit of secular rulers, right? Can the Pope just take days out of the calendar? Things of that nature, of course, have to be addressed because if a year is shorter, that will have repercussions for tax collections, for the validity of contracts. There are all sorts of repercussions that follow from

that. And these problems, to a large extent, explain why it takes 400 years for a decision to be definitively made and for steps to be taken. And that takes us to the Council of Trent in the second half of the 16th century. It takes us to the time of the Counter-Reformation and finally to the papacy of Gregory XIII, who felt that he had the authority and the influence and the means necessary to make sure that Catholic rulers, at least, would go along with whatever reform he proposed. Given that length of time it takes to get to that point, Philip, I'm guessing it also takes a lot of time for then that official announcement, like this change, this reform, to diffuse, to spread across the world. Yes, it takes a long time. It usually dates the Gregoirean reform to 1582, but in fact, most territories which adopted this new calendar only did so in the subsequent years.

And of course, if you look at the bigger picture, some of them only in the 18th, 19th or early 20th century. It takes a long time precisely because of the political fragmentation of the Christian world, because of the schism between Protestants and Catholics, also the schism between the Catholic Church in the West and the Orthodox and Eastern churches further afield, right? So there's, of course, no unanimity. But at least Gregory XIII could count on the loyalty of Catholic rulers in his time. And he could also count on the logistics being available, print technology and communication avenues that made it possible to disseminate the new calendar and make sure everybody knows what the new rules are supposed to be. That in and of itself would have been a

huge challenge only a century or two earlier in a pre-print world. Ah, of course, the coming of printing and all of that. I mean, is there anywhere in the world today, as we're now so used to the Gregorian calendar, is there anywhere that Julius Caesar's Julian calendar is still in active use? Yes. So if you look at the Orthodox and Eastern Apostolic churches, it's a bit of a complicated patchwork, but there are so-called old calendarists in these various churches and Christian spheres where the old Julian calendar is still used, and others have adopted usually a different version of the Gregorian calendar, which is to say that they went along with the elimination of days from the Julian calendar, but they implemented a slightly more astronomically sophisticated leap year rule in order not to be accused of simply copying the Gregorian calendar.

And in fact, the introduction of this new Julian calendar or reform calendar early in the 20th century was a cause of schism and conflict within Orthodox churches in Greece and Russia and other parts of the Eastern Christian world. I mean, we think, I know, Ida, you think some of the Judaizers, you think of this warrior figure of the late Roman Republic, this tyrannical figure, this great warlord, renowned for his campaigns, for his battles, for his politics. But can we say actually one of the greatest legacies, one of the longest lasting legacies of Julius Caesar is all to do with time and this calendar? I think that's undoubtedly true, yes, especially if you just look at political reforms. That's

the one that really stayed. Of course, if you think of Caesar as a military general, then I think his conquest of Gaul and his winning the Civil War had repercussions that were just as important in the long term. But as a politician, I think that conquest of Gaul and his winning the civil war had repercussions that were just as important in the long term. But as a politician, I think that's his most lasting legacy for sure. One last question from me, and it's kind of going on a tangent. But Philip, I'm a big Alexander the Great and Hellenistic successors fan. That's my area of interest. puzzled me, interested me, is that sometimes in this period, let's say Hellenistic period or the classical period, you get certain events that have a particular date attached to them, saying this

event happened on this date. And a good example would say the Battle of Galgamela. Apparently there's a lunar eclipse 10 days before and people have been able to date that eclipse. So then say the battle occurred 10 days later on the 1st of October. Now, with the whole changing of the calendars and the different calendars that we've had over these past two millennia, two and a half millennia, how accurate is it that we can say, like, even if they mention a lunar eclipse or something, that this happened on this day today? Yeah, it's perfectly accurate. And part of the reason why this works so well, these computations of ancient eclipses, is because astronomers today use a proleptic Julian calendar. They use Caesar's calendar projected into the distant past. I mean, there's also a Julian day count, which counts the days successively or in sequence from a date, I think, in 4714 BC. But it's all based on the assumption that the Julian

calendar existed before it actually existed. That's sort of the framework within these astronomical computations that are performed to this day. So astronomy to this day still uses the Julian calendar to... Wow, amazing. Once again, that long-lasting legacy. Philip, it's been a joy to get you on the podcast. Last but certainly not least, you've written a book all about the Julian calendar, the Gregorian calendar, and all of that. That is true, yes. My book is called Scandalous Era, which was published by OUP in 2018.

And it essentially tells the story that got us from Julius Caesar to the Gregorian reform of 1582, everything that happened in between, essentially. Brilliant. Well, Philip, thank you so much for taking the time to come on the podcast today. Big pleasure. Thank you. I hope you've enjoyed this episode all about how Julius Caesar changed time. I'll be honest, I absolutely love that title. It's such an awesome episode to finish off 2021 on. I mean, what a year it's been, but bring on 2022.

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