science

Roman timekeeping

Roman timekeeping is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Roman timekeeping rather than just read about it. In short: In Roman timekeeping, a day was divided into periods according to the available technology. Initially, the day was divided into two parts: the ante meridiem (before noon) and the post meridiem (after noon).

Key takeaways

Roman timekeeping belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Roman timekeeping to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Roman timekeeping from memory before moving on to harder problems.

Reference excerpt

In Roman timekeeping, a day was divided into periods according to the available technology. Initially, the day was divided into two parts: the ante meridiem (before noon) and the post meridiem (after noon). With the introduction of the Greek sundial to Rome from the Samnites circa 293 BC, the period of the natural day from sunrise to sunset was divided into twelve hours.

Variation An hour was defined as one twelfth of the daytime, or the time elapsed between sunset and sunrise. Since the duration varied with the seasons, this also meant that the length of the hour changed. Winter days being shorter, the hours were correspondingly shorter and longer in summer. At Mediterranean latitude, one hour was about 45 minutes at the winter solstice, and 75 minutes at summer solstice. The Romans understood that as well as varying by season, the length of daytime depended on latitude.

Subdivision of the day and night

Civil day The civil day (dies civilis) ran from midnight (media nox) to midnight. The date of birth of children was given as this period. It was divided into the following parts:

Media nox (midnight) Mediae noctis inclinatio (the middle of the night) Gallicinium (cock crowing) Conticinium (cock stops crowing) Diluculum (dawn) Mane (morning) Antemeridianum tempus (forenoon) Meridies (mid-day) Tempus pomeridianum (afternoon) Solis occasus (sunset) Vespera (evening) Crepusculum (twilight) Prima fax (lighting of candles) Concubia nox (bed-time) Intempesta nox (far into the night) Inclinatio ad mediam noctem (approaching midnight)

Natural day The natural day (dies naturalis) ran from sunrise to sunset. The hours were numbered from one to twelve as hora prima, hora secunda, hora tertia, etc. To indicate that it is a day or night hour, Romans used expressions such as for example prima diei hora (first hour of the day), and prima noctis hora (first hour of the night).

Timekeeping devices

The Romans used various ancient timekeeping devices. According to Pliny, Sundials, or shadow clocks, were first introduced to Rome when a Greek sundial captured from the Samnites was set up publicly around 293-290 BC., with another early known example being imported from Sicily in 263 BC. Despite rapidly gaining popularity soon after their introduction, it wouldn't be until 164 BC that the first sundial specifically designed for the city of Rome was constructed. The main disadvantage of sundials were that they worked only in sunshine and had to be recalibrated depending on the latitude and season. For this reason, they were often used as a method to calibrate water clocks, which could always tell the time, even on cloudy days and at night.

Legacy The Roman day starting at dawn survives today in the Spanish word siesta, literally the sixth hour of the day (sexta hora). The daytime canonical hours of the Catholic Church take their names from the Roman clock: the prime, terce, sext and none occur during the first (prīma) = 6 am, third (tertia) = 9 am, sixth (sexta) = 12 pm, and ninth (nōna) = 3 pm, hours of the day. The English term noon is also derived from the ninth hour. This was a period of prayer initially held at three in the afternoon but eventually moved back to midday for unknown reasons. The change of meaning was complete by around 1300. The terms a.m. and p.m. are still used in the 12-hour clock, as opposed to the 24-hour clock.

Illustrations

Worked examples

Example 1 — a first encounter with Roman timekeeping

Start with the simplest possible case. Write down what Roman timekeeping claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Roman timekeeping before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Roman timekeeping ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Roman timekeeping

In research: Roman timekeeping appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Roman timekeeping in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Roman timekeeping is common in secondary-school and first-year university syllabi. It links to neighbouring topics Ancient Roman units of measurement, History of timekeeping, Time measurement systems, so understanding it makes those chapters shorter.
In everyday life: Look for Roman timekeeping outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Roman timekeeping in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Roman timekeeping means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Roman timekeeping out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Roman timekeeping in simple terms?

Why does Roman timekeeping matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Roman timekeeping?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Roman timekeeping.