Timekeeping In The Roman Army

Cultural Perspectives • 07 Jul 2018

Timekeeping In The Roman Army

by Professor George Cupcea

Time measurements in Ancient Rome

Keeping time in antiquity was no small feat. The fact that the Romans were able to know the time down to the hour is quite impressive and it played a key role in the organisation of the inimitable Roman military machine. Looking back at the advancements made in horology, scholars of Greek and Roman antiquity rely heavily on ancient literature, epigraphy (and/or papyrology) and archaeology in order to form a cohesive view of the evolution of time and timekeeping. The scarcity of sources and the lack of ample technical documentation see it that any new findings are open to rigorous debate and scrutiny. Nevertheless, it is a topic of key importance for horology, as it was a period when much of the groundwork was laid for artisans to build on and further develop.

The march of the Roman army over the Danube, 101 CE, Trajan’s Column

Beginnings: Sun and Water

In the very beginning, the Romans didn’t measure time in minutes or seconds, the smallest unit was the hour. Irrespective of the season, day and night were divided into 12-hour periods. Each requiring its own specific equipment to gauge an approximation of the time. Inspired by the Greeks, these rudimentary clocks relied upon on either the sun or the water. The first being the sundial (called the Horologium), used during sunlight hours, although it was as one would expect rather useless during night time and on cloudy days. Used in interiors, during the night and on cloudy days, the second popular piece of equipment was a bowl of water with a small hole in the bottom. Called the Klepsydra, which was most likely borrowed from Greek law courts would indicate a pre-determined length of time by the duration it took for the water to empty from the bowl. Unlike the sundial, the Klepsydra was developed and adapted to account for the seasons and latitude.

Reconstruction of a klepsydra from the 5th c. BCE,  Ancient Agora Museum in Athens

Under these conditions, the ancient clocks were at best an approximation of time. A far cry from the accuracy of modern methods of timekeeping. Despite this, these early efforts were revolutionary in comparison to the alternative of looking to the position of the sun in the sky.

Keeping Time for the Elites

The Roman conquest of what we now know as Italy was the beginning of their foray into horology. Encountering the technically advanced Greeks in the South, the Romans heavily borrowed technology encountered on their expeditions across the Mediterranean. On one occasion, a Sundial was taken from Sicily where it was then displayed in Rome and continued to be used incorrectly for 99 years. This didn’t seem to cause terrible concern for the general population though. As, up until the third and second centuries BCE, the Romans were more likely to need general indications of the time of day rather than precise and detailed ones. The establishment of a more accurate sundial calibrated to the latitude of Rome was hailed as a worthy achievement and significant leap in region-specific timekeeping.

The sundial of Interamna Lirenas, Italy, dedicated by the newly elected Plebeian Tribune M. Novius Tubula, 1st century BCE

Around one hundred instances of clocks (generally referred to as horologia) are found in stone inscriptions across the Mediterranean. Found in both Greek and Latin, the majority (more than 90%) are found in civilian environments across the western provinces of Italy. Oftentimes part of a larger monument or public building complex, the most famous instance of a clock from antiquity is the Andronicus’ Tower. Nowadays referred to as the ‘Tower of the Winds’ in Athens, it is dated back to the 1st century BCE and was considered an extremely important artefact, as evidenced by elaborate decorations found on the exterior of the building.

Tower of the Winds, Agora, Athens

Yet despite the public placement of these clocks, time was still the purview of an elite few who possessed the adequate knowledge required to understand and interpret the significance of these artefacts. Roman Architect, Vitruvius argued that despite there being no shortage of information for the construction of portable clocks, construction was limited by one’s understanding of the analemma (the skeletal celestial sphere). Thus, for the public, the barriers remained prohibitively high. For many years, timekeeping was a luxury of the elite.

Vitruvius Pollio (80-15 BCE) presenting ‘De Architectura’ to Augustus

Epigraphic evidence suggests that there were workshops and craftsmen dedicated to the fabrication of clocks. Inscriptions indicate the presence of workshops with highly specialized craftsman, charged with making timekeeping devices. Magistrates, especially consuls, usually paid for their construction and they were intended to be installed in the prominent political and juridical areas of the city, therefore bearing, at least initially, an exclusively political role.

It wasn’t until the between the 6th and 5th centuries that concerns for a more scientific approach of timekeeping emerged, one that would consider and pay more attention to the cosmos and the calendar. Nevertheless, as with many innovations, the pursuit for more accurate timekeeping had scientific motivations as well economic and militaristic underpinnings. The effectiveness of the Roman military machine is due in part to their reliance on timekeeping to fragment and organise the day.

Timekeeping in the Roman Army

Since the establishment of a professional soldiery and semi-permanent provincial garrisons, dividing the day into hour increments was of paramount importance for the Roman army. The unity of the military machine was admirable despite the rudimentary methods for approximating time. Military units woke, ate, marched and slept at pre-defined times. Infantry units, for example, were required to march twenty miles in fiver summer hours. Even with unexpected alterations, the highly organised program found room to adjust.

Lucius Cornelius Sulla (138-78 B.C.) and his army fighting their way into Rome in 82 B.C. enabling Sulla to become Dictator. Wood engraving, 19th century.

We know of few accounts in ancient sources relating to precise timekeeping in the army. Josephus notes that action was planned by the hour, when describing Titus’ siege of Jerusalem. Polybius argues that an ideal commander must be able to tell the time of the day to ensure success in any given campaign. However, as no actual mention of a sundial or water clock appears in these instances we might assume that astronomical reckoning is used. A classic example of the relativity of actual timekeeping is the battle of the Colline Gate in 82 BCE, at the end of Sulla’s Civil War, where ancient sources give approximate and sometimes contradictory time relations (Appian – late in the afternoon; Plutarch – at the fourth hour/daybreak). On the other hand, Julius Caesar in 54 BCE acknowledged that night hours are shorter in Britain than on the continent, conducting his measurements with a water-operated timepiece.

Dividing the Day and Tracking Soldiers

The best-known instance of temporal organization inside the Roman army is the night watch (vigiliae), the night was divided into four equal parts of three hours each, with the help of the Klepsydra. As for daylight hours, a series of newly published ostraka from the Krokodilô fortlet in Egypt sheds some light on tracking personnel based on log times. Contained within the daily registers are the arrival and departure times of soldiers and messengers at a military post station.


The Night Watch – “vigiliae” Credits: Wikipedia

For each day and each messenger, the time of arrival, the source and content of the package and the time of departure are registered. The sources present different hours in the day, telling us that timekeeping was an exact matter in this situation, and was most likely the task of the curator, using a water clock. Giving quite an accurate indication of the level of organisation present at what could be considered a small post of only 10 to 15 soldiers (at any given time). A recently discovered bronze fragment from Vindolanda is another fine example of the need for chronological unity across an army. Etched into the fragment is a series of time markers, most likely used to keep track of soldier movement from post to post.

The calendar fragment of Vindolanda

In at least two cases a horologium is mentioned in a military context, and in another four the soldiers responsible for building and looking after the official clock – the horologiarius. The first example qualifies as circumstantial evidence. It is a sundial discovered in Si‛â (Syria), with an inscription that mentions its owners/builders, two legionaries of VIII Augusta. The second example from Rigomagus in Lower Germany, stating that in the time of the Caesar Diadumenianus (218 CE), the official clock of the fort malfunctioned and collapsed due to old age. It was reconstructed at the expense of the unit commander and provincial governor. It can be assumed that no time was wasted in the reconstruction. Timekeeping was and continued to be extremely critical in the planning and organisation of military units.

The Solarium Augusti with the obelisk as gnomon

Modern watchmaking bears little (at face value) resemblance to timekeeping in ancient Rome. However, as evidenced above the method of telling the time in the ancient world incorporated both highly specialised scientific and technological methods as well as artistic and decorative techniques. Horology has evolved significantly, yet at its heart it has remained the same. Horology then and now (and especially watchmaking) is a beautiful representation of the unique relationship between science and art.

Tags: ancient timekeeping horologium hourglass klepsydra roman army roman timekeeping rome sun clock sundial vigiliae water clock

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