~ Curious And Unusual ~
- 8 -

Mid-day in Rome

the city's official timing



How can you tell what time it is?
You would obviously take a look at your watch. But if your watch was wrong, or had it stopped, you would need to ask somebody the time, or take a look at a clock, that is you would need to use a reliable reference.

In the Classic Age this was not a problem, as there was no such thing as official timing. Even measuring the day in hours was something the Romans started handling rather late, compared to other civilizations.

variation in length of the Roman dies
(daylight hours, in yellow) over the year
Apparently, the earliest sundial (solarium) appeared in Rome between 300 and 260 BC, being set in the Forum, by the Rostra. But since it had been imported from Greece, it was not calibrated properly for the local latitude, so it proved inaccurate. It was only replaced about one century later.

In ancient Rome the day was divided into two parts, dies (hours of daylight) and nox (hours of darkness); the latter was not considered as a real part of the day, but rather as a sort of 'gap' that separated one dies from the following one.
The daylight hours (horae) were twelve, divided into tempus antemeridianum (antemeridian time) and tempus pomeridianum (postmeridian time) by the central part of the day called meridies. Their duration, though, was rather variable, as the daylight in late June (summer solstice) spanned from 4:30 am to 7:30 pm, about fifteen hours, but in late December (winter solstice) it lasted from 7:30 am to 4:30 pm, about nine hours. And since the length of the horae was the twelfth part of the daylight period, an hour could last from a minimum of 45 minutes to a maximum of one hour and fifteen minutes.
The Roman sundials were based on a scheme of lines that divided twelve sectors of variable size, crossed by further lines, no less than three, the central one marking the equinoxes, while the others (curve in shape if the sundial was drawn on a flat surface) marked the solstices.
For military reasons, the night too was divided into four periods called vigiliae, each of which about three hours long, consistent with the guard duty of the sentries. And the dies was in fact divided according to this scheme into four similar periods of three hours each, the hora tertia, the hora sexta, the hora nona, and the hora duodecima (or vespera).
For measuring time during the hours of darkness, hourglasses filled with water (clepsydrae) were employed; they were also used during daytime, both in public offices and in private houses (in wealthy ones, keeping account of the time and announcing the hours was a servant's duty).
It should be noted that in mentioning time (prima hora, secunda hora, etc.) the Romans referred to the hour that was passing, i.e. not yet completely elapsed, unlike today's custom.
Such division of the day into two parts made of four periods, each of which including three hours, was maintained during the Middle Ages, where it gradually turned into the canonical hours, divided into eight periods of prayer called Invitatory, Matins, Lauds, Terce, Sext, None, Vespers and Compline (yet no longer matching exactly the military turns of the Roman guards).

← in hemispheric sundials the light entered from a hole above, reaching the twelve sectors;
the line marked E indicates the equinoxes, the line marked S the summer solstice

When mechanical clocks first appeared in Europe (13th century), the main churches started having their own; the people could now rely on the bells that struck the hour. But the clocks were not well synchronized, and the bells often rang at different times.
So was in Rome, as well, where the situation remained unchanged until the turn of the 18th century, because an official time reference for all the city was still lacking. This may have been the thought of pope Clement XI, when he commissioned to astronomer Francesco Bianchini the making of an important and complex sundial for the basilica of St.Mary of Angels and Martyrs (commonly shortened in St.Mary of Angels, or Santa Maria degli Angeli).
The same pope also took care that the instrument visually marked the limits within which the day of Easter should fall, a date that changes every year, which the first Council of Nicaea (AD 325) had fixed as the Sunday that follows the first full moon after the spring equinox.

Michelangelo turned the remains of the ancient
Baths of Diocletian into the church of St.Mary of Angels
Therefore, the sundial was not built by Clement XI to act as only a standard time reference for the city, but also as an astronomical and religious calendar.


(↑ above) the right arm of the church's transept;
a red circle indicates the sundial's lens;

(↓ below) ellipses show the position of the North Star,
while the long line of the sundial stretches at the back
The church of St.Mary of Angels was chosen as a proper site for the sundial because the building is rather imposing, therefore it was considered strong enough not to move in the case of an earthquake: its steady floor would prevent the notches along the line from shifting, thus making the time measurement fully reliable.

This church is also famous because it was built over the remains of the great baths of emperor Diocletian (finished in AD 305); their surface was over 360 × 370 metres in size (about 400 × 410 yards), and the church, despite being one of the largest in Rome, now covers only a small part of this area.

the sundial's lens in detail; the marble
cornice below was cut in order to let the
light beam reach the line on the floor
Michelangelo drew the project of St.Mary of Angels (1563) in order to use the surviving central halls of the ancient complex, with their original columns. The same façade of the church is in fact a tall niche, or exedra, belonging to the old Roman structure.

Clement's sundial was unveiled in 1702, and still today it stands on its original site. The lens has the shape of a large papal coat of arms, that hangs above the wall of the right arm of the transept, at a height of about 20 metres (65 feet), with a hole in its central part: at mid-day, a ray of light passes through the lens, reaching a very precise scheme, consisting of a long bronze line (known as the Clementine Line) inlaid in a wider marble band that crosses the floor of the church stretching for 44 metres (about 145 ft).

Along both sides of the line are also ten panels of inlaid marble featuring the zodiac signs (drawn by Carlo Maratta, a distinguished painter of the late 1600s, who is buried in the same church); the two ones featuring Cancer and Capricorn, instead, are located at the two opposite ends of the line, as the light falls on them respectively on summer soltice and winter solstice, i.e. the two times of the year when the ray of light coming through the lens is shortest and longest.
A large mark along the line reading Terminus Paschae is the date limit Easter day must fall within, while minor lines and notches indicate other astronomical observations.

Immediately below the first panel is a series of concentrical ellipses that indicate the position of the North Star, from year 1700 to year 2100 (only Jubilee years are shown).

panels with zodiac signs Gemini and Leo
and the mark on Easter Day's limit →

left and below: further panels featuring zodiac signs Cancer, Virgo, Pisces, Scorpio;
the first one marks the bottom of the line; the last one is smaller as its position coincides with one of the columns

Clement XI's sundial acted as Rome's official time reference for about 150 years; today modern astronomers keep considering it a unique wonder of its kind, as it is still precise as when it was built.
Interestingly, the ray of light of this sundial does not touch the line at 12 o'clock sharp, as most people would expect, but at the so-called solar mid-day, which is the very moment of the day when the rising phase of the sun changes to the setting phase (the scheme on the left should help to understand this concept). This moment occurs at different hours depending on several parameters, such as the day of the year and the exact geographic position of the sundial, in terms of latitude and longitude. In other words, when it is 12 o'clock anywhere within a given time zone (as time zones are based on a convention), the actual position of the sun differs according to each specific place. In the diagram, the solar mid-day takes place at 12 o'clock over spot B, but on spot A it takes place sometime earlier, i.e. before the standard mid-day, and on spot C sometime after the standard mid-day.
This is a simplified situation, as during the year also the solar mid-day over spot B would take place at different times, from day to day.

The table on the right (calculated for Rome and referring to year 2011) shows at what time the solar mid-day (red line) takes place compared to the standard mid-day. The mismatch throughout the year can range from 6 minutes before 12 o'clock (at the beginning of November) to 25 minutes after the same time (in mid February). The two mid-days very shortly coincide in early October and early December: these are the only two times of the year when the ray of light of St.Mary of Angels's sundial touches the Clementine Line exactly at 12 o'clock.


In those days, though, 'mid-day' was still merely considered an astronomical event: in fact, the people in Rome used to count the hours of the day from the last religious function which all churches in the city held at a given time. The function, called by locals Avemmarìa (i.e. the Ave Maria prayer), acted as a time reference for the rest of the evening, and for the following day; expressions such as "at twenty-one hours" actually meant twenty-one hours after the function (i.e. in the afternoon of the following day).

conversion table of the timing system
in Rome until the mid 19th century
Things were complicated by the fact that the evening prayer was held at about 7:15 PM, but during winter it was brought forward at 6:15 PM: therefore, "at fifteen hours" meant a quarter past ten in June, but a quarter past nine in January.

This was not the only complication of Rome's timing. When clocks finally began to appear on important churches and public buildings, some of them had a dial with only six hours, not twelve as in ordinary clocks, so to divide the day into canonical hours, when the prescribed prayers were to be recited. The bells, instead, rung up to twelve times, despite the dial, and the hours were counted up to 24! For instance, at the 21st hour (i.e. around 4 pm in summer) the dial would have shown III, and nine tolls of the bell would have been heard.
Only very few of these dials are still extant (see pictures on the right).


the dials in the Cortile del Commendatore
(complex of Santo Spirito in Sassia) and
on the front of Santa Maria dell'Orto's church

Today's ordinary system once used to be called 'French timing', as it was temporarily introduced by the end of the 1700s, when Rome was occupied by Napoleon's troops and was administered by the French empire. The population did not feel very comfortable with the change, and when the papal rule was restored in 1814, the old 'Roman timing' was taken back into use.

No sooner than the second half of the 19th century, pope Pius IX definitively switched to the 'French timing', and in Rome too mid-day became the main reference from which the hours of the day were officially counted, replacing the religious timing method.

Furthermore, since the bells kept ringing at different times despite the sundial, in order to avoid confusion, the same pope introduced the custom of publicly announcing mid-day throughout the city in a rather curious way: as of December 1st 1846, every day at 12 o'clock, a cannon was fired from the top of Sant'Angelo Castle, striking the official time.

← the astronomical tower over the Roman College building

Meanwhile, other sundials had been built in Rome: one of them was housed in a small tower built in 1787 above the Roman College, Rome's main Jesuit seminary, which also housed in one of its wings the old astronomical observatory.
By that time, mid-day was being officially measured from the aforementioned tower (picture above). The roof of the nearby church of Sant'Ignazio di Loyola was fitted with a tall pole along which ran a sphere, large enough to be seen from the castle (about 1,300 metres or  mile away). A few minutes before 12 o'clock the sphere was raised to the top of the pole: this was a sign for the soldiers in the castle to get ready. Then, as soon as the sundial in the tower marked mid-day, the sphere was abruptly lowered, and the cannon was promptly fired from the castle. Already in those days, people used to gather by Sant'Ignazio's church, to enjoy this ceremony.

view from the astronomical tower, in a picture of the 19th century: →
the sphere (arrow) can be seen at the top of the pole on Sant'Ignazio's roof
Very soon the daily shooting of the cannon became such a popular custom that when the French troops sieged Rome in 1849, during the days of the Roman Republic, the first cannon-shot against the city was actually mistaken by several people for the mid-day signal!
This tradition was maintained in time, also when more modern methods of measuring mid-day than a simple sundial came into use.
In 1903 the location of the gun-shooting ceremony was moved to Monte Mario, a hill on the north-western side of the city, but then, having this location been reputed too distant from the city center, only one year later it was moved again to the top of the Janiculum Hill, the highest spot within Rome's historical districts.
The daily gun-shot was stopped during World War II, but in 1959, on April 21st (the day traditionally believed to be "Rome's birthday"), the ceremony was resumed. Since then, it has never been discontinued again: still today, in the age of precision quartz watches, the firing of the Janiculum's gun is a popular daily event for Roman people.

← the cannon ceremony at mid-day


↑ for every child in Rome
the cannon ceremony is a must


the panoramic view over Rome
from the Janiculum Hill →
Especially on weekends, crowds of children and tourists gather by the famous balcony on top of the hill, excitedly awaiting for the cannon to be rolled out: on a small terrace below, just in front of the breathtaking view over the city, three soldiers ritually load a howitzer, and after a short countdown they fire a blank shot, at 12 o'clock sharp.
The blast is so loud that it can be clearly heard throughout the centre of Rome. Despite nowadays the noise of the heavy traffic may sometimes cover it, the locals still check their watches to the sound of the peculiar time alarm from the Janiculum.