Lilian and Julian

Are you ready already for another New Year?

Today is January 14. But it’s January 1 in the Julian calendar, which still lingers in a few ways.  It is the calendar that European-type countries used from 45 BC, when Julius Caesar imposed it, till 1582, when Pope Gregory XIII replace it with the Gregorian calendar by which we now live.

These pontiffs did not do the inventing of their calendars. (Yes, Caesar too was a pontiff; he was dictator at the time, but to rule on such matters he used another office he held, that of pontifex maximus, literally “greatest bridge-builder,” a sort of chief priest.)

My painting of a sculpture of Julius Caesar.

His adviser on the calendar was Sosigenes. Sosigenes was one of the Greek scholars from Alexandria in Egypt, so he knew about the shortcoming of the 365-day Egyptian calendar which had been used till then. There are only two scraps of information about Sosigenes, both from the Natural History of Pliny the Elder: that he was an “experienced scientist” who helped Caesar to “bring the years back into agreement with the Sun,” and that he stated that Mercury moves no more than 22 degrees from the Sun. It could be that the method for correcting the calendar with leap-days had been proposed centuries earlier by Eratosthenes or Aristarchus, and Sosigenes was reviving it.

And if calendars were named for the brains behind them, our present one should be called not Gregorian but Lilian. Luigi Lilio (in the style of the time he Latinized his name as Aloysius Lilius) was the “first author” of the new calendar, which his brother Antonio presented to the pope in 1575. Luigi died in 1576, and the proposal went through rounds of study by committees, and slight modifications, before it could be adopted in 1582. By then the intellectual leader of the process had become Christopher Clavius, a German Jesuit and mathematician. Clavius was candid in giving all credit to “Luigi Giglio.” And yet it is commonly stated, without mention of Lilio, that Clavius devised the calendar; I see I’ve put it that way myself in the “Calendars” section of the Astronomical Companion (I’ll make up for it if I can do a third edition), which is why you may have expected me to say that our calendar should be called Clavian.

“Julian” is the name that seems to have (as we’d say now) “gone viral.”

The Julii were just one of the patrician families of Rome. A gens was a family; this family was the Gens Julia, “Julian family”; a name such as Gaius (or Caius) Julius Caesar consists of a praenomen or personal forename, a nomen or family name, and a cognomen, which might be a branch of the family or some other way of distinguishing people with the same praenomen.

And there had been, in old republican Rome, many famous leaders, such as the Gracchus brothers, Cincinnatus, the Scipios, Cato, Marius, Sulla. Some had been allowed to be dictator in time of national crisis. But there was a revulsion from the idea of “king” ever since Rome had got rid of its early dynasty of Etruscan kings. Then C. Julius Caesar made himself so powerful (by being in charge of the conquest of Gaul and then by outmaneuvering his colleague and rival Pompey) that he did “bestride the narrow world like a colossus,” appeared to be about to become king, and was therefore assassinated. In the subsequent strife, Gaius Octavius, who came from a plebeian family but was a maternal great-nephew of Caesar and had been adopted as son in Caesar’s will and thus became Gaius Julius Caesar Octavianus, rose to the top and became the Imperator Augustus: not just a “commander,” as imperator had meant, but the first of hundreds (I think) of Roman emperors – it depends whether you count co-emperors, emperors of the east, Holy Roman emperors of Germany…

In effect these two, Julius Caesar and his “son” Augustus, re-created the kingship, and then some. A parallel is France, whose revolution erased the hated monarchy and aristocracy, and yet monarchy soon returned in the form of the Emperor Napoleon and kings Louis Philippe and Napoleon III; and princesses and marquises soon again abounded. And Islam, whose founder did not make himself king, so he was succeeded only by a khalîfah, “deputy” or “successor”; yet the line of caliphs became emperors (the second dynasty of them, the Umayyads, who sprang from the pre-Islamic establishment, are particularly despised by the Shî’ah as mulûk, “kings”).

Julius and Augustus got their names into our calendar of months; Caesar became Kaiser and Tsar; I don’t feel anybody can greatly like C. Julius Caesar and yet it’s from him that Julius and Julia are among the commonest given names, and there’s Julie and Julian and Juliet, and juliet balconies.

And back in the matter of calendars, the proliferation of Julius is a nuisance. There is not only the old Julian version of the common calendar, but the useful system of Julian Days. It ignores years, months, hours, and minutes, and counts just days, from 4713 BC Jan 1 (in the Julian calendar, 4714 Nov. 24 Gregorian – you see the confusion already). Thus today, 2015 Jan. 14, is JD 2457037. Finding the number of days from 2000 Jan. 1 to 2015 Jan. 14 is much more difficult than subtracting JD 2451545 from 2457037. This system is used by all who do calculations in astronomy (and some other fields such as the food industry): we translate dates into JD, do the calculating, and translate back into the usual messy several-term dates.

Now this system was also proposed (in 1583) as a side-contribution to Pope Gregory’s calendar reform. It was proposed by Joseph Scaliger, a French Protestant scholar. And he named it Julian, in honor of his own father, Julius Caesar Scaliger. Damn! It has nothing to do with the Julian calendar, which was being swept away at that time. Why couldn’t he have named it Scaligerian? The Latin name his family had taken means “ladder-bearer,” and what an appropriate name that would be for this long even ladder through time!

Nothing, I’ve learned, is as simple as what I first learn about it. Scaliger’s proposal was not the simple counting of days, but a cycle of 7980 years, the lowest common multiple of three other cycles, and he thought it would be useful in history. It did start at 4713 BC. It was John Herschel in 1849 who suggested the count of days from the beginning of Scaliger’s Julian Era. And, Scaliger did not call it Julian after his father, but because he thought it fitted well enough with the years of the common calendar, which he apparently still thought of as the one founded by Julius Caesar.

Back to Sosigenes (and I won’t push for renaming the Julian calendar “Sosigenean” either).

His other known accomplishement was observing Mercury, or at least he was one of the authorities for the statement that Mercury moves out no more than 22 degrees from the Sun. (The other was Cidenas, as the Greeks called the Babylonian astronomer Kidinnu.) That’s a good average, but Mercury’s maxima of elongation, or angular distance from the Sun, can be as little as 17.9 and as great as 27.8 degrees.

Today Mercury reaches one of its peaks of eastern elongation: 18.9 degrees. It’s a below-average extreme of elongation, but the angle is favorable for the northern hemisphere, so Mercury stands about 15 degrees above the Sun.


Comparing this after-sunset view of the western horizon with that of Jan. 9 (see “Quasi” in the list of posts at right), you can see that Venus is getting away, slowly as yet, from Mercury’s almost-conjunction with it of five days ago.


7 thoughts on “Lilian and Julian”

    1. Well, the Romans used a letter, I, which later became our I and J. (They wrote in what we now call majuscule or capital letters.) I was for both a vowel as in “pin” and a semivowel as in German “ja” or English “yet.” And V, also, was for a semivowel, like the beginning of “wet,” and a vowel as in “put”; our letters U, V, and W all derive from that letter. So when we write “Julius” we’re sort of modernizing “IVLIVS.”

      This is all a bit dry, I know, and I thought of illustrating it with a wonderful bit of Latin poetry that I discovered, about love. But I think that shouldn’t be hidden down here in a reply to a comment so I’ll make a small blog post out of it – but maybe after the next one, after something more serious.

  1. What a wonderful ramble through history. Thanks Guy, and happy Julian new year to you!

    I’m very fond of the lunar crater Clavius, but I’ve never bother to find out who it was named after. Sure enough, Christopher Clavius.

    Clavius the crater is nearby the more famous Tycho crater. Tycho is one of the most easily recognized craters around the time of full Moon, because Tycho is a young crater with prominent rays that spread across much of the visible surface of the Moon. But Tycho is a relatively small crater compared to Clavius, which is one of the biggest craters on the Moon. When they are both near the terminator during the waxing or waning Moon, Clavius is big and obvious, while Tycho takes some hunting to identify.

    From wikipedia I learn that Clavius the astronomer (1538 – 1612 AD*) was a German Jesuit mathematician and astronomer and in his later years probably the most respected astronomer in Europe. Although Clavius was a staunch geocentrist, even Galileo, who treated most everyone contemptuously, was solicitous toward Clavius.

    *Given that Clavius was a Catholic priest, “AD” seems more appropriate than the currently more politically correct “CE”.

      1. Lilius the crater is small and not too far from Clavius. Lilius is labeled on my one-page Sky and Telescope Moon map, so I should be able to identify it through my little telescope. But the southern highlands are carpeted with craters and it’s easy to get lost. I doubt I’ll be able to find Lilius, but I’ll try next moon-month.

    1. Good question.
      The three time cycles of which Scaliger wanted to find a common multiple were:
      – The Metonic cycle of 19 years (after which Moon phases return to the same month-day date).
      – The “Solar” cycle of 28 years (after which weekdays repeat on the same month-day dates – in the Julian calendar, that is).
      – The Indiction cycle of 15 years (no astronomical significance; a medieval practice of dating documents; e.g. our year 2015 is year 8 of an indiction.).
      This is Scaliger’s “Julian Period.” Going back in time, the last year in which all three cycles began together was 4713 BC (Julian). So Scaliger suggested that as a convenient era from which to date events, because it was before all known historical events. (Including the Creation?)

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