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 Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

sundial A sundial is a horology, horological device that tells the time of day (referred to as civil time in modern usage) when direct sunlight shines by the position of the Sun, apparent position of the Sun in the sky. In the narrowest sense of the ...

to Rome from the

Samnites The Samnites () were an ancient Italic peoples, Italic people who lived in Samnium, which is located in modern inland Abruzzo, Molise, and Campania in south-central Italy. An Oscan language, Oscan-speaking Osci, people, who originated as an offsh ...

circa 293 BC, the period of the natural day from sunrise to sunset was divided into twelve

hour An hour (symbol: h; also abbreviated hr) is a unit of time historically reckoned as of a day and defined contemporarily as exactly 3,600 seconds ( SI). There are 60 minutes in an hour, and 24 hours in a day. The hour was initially establis ...

Variation

An hour was defined as one twelfth of the

daytime Daytime or day as observed on Earth is the period of the day during which a given location experiences Daylight, natural illumination from direct sunlight. Daytime occurs when the Sun appears above the local horizon, that is, anywhere on the ...

, 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 The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern ...

latitude, one hour was about 45 minutes at the

winter solstice The winter solstice, or hibernal solstice, occurs when either of Earth's geographical pole, poles reaches its maximum axial tilt, tilt away from the Sun. This happens twice yearly, once in each hemisphere (Northern Hemisphere, Northern and So ...

, and 75 minutes at

summer solstice The summer solstice or estival solstice occurs when one of Earth's poles has its maximum tilt toward the Sun. It happens twice yearly, once in each hemisphere ( Northern and Southern). The summer solstice is the day with the longest peri ...

. The Romans understood that as well as varying by season, the length of daytime depended on

latitude In geography, latitude is a geographic coordinate system, geographic coordinate that specifies the north-south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from −90° at t ...

Subdivision of the day and night

Ancient Roman time keeping hora vigilia equinox solstice

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,

Sundial A sundial is a horology, horological device that tells the time of day (referred to as civil time in modern usage) when direct sunlight shines by the position of the Sun, apparent position of the Sun in the sky. In the narrowest sense of the ...

s, 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 Sicily (Italian language, Italian and ), officially the Sicilian Region (), is an island in the central Mediterranean Sea, south of the Italian Peninsula in continental Europe and is one of the 20 regions of Italy, regions of Italy. With 4. ...

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

and season. For this reason, they were often used as a method to calibrate

water clock A water clock, or clepsydra (; ; ), is a timepiece by which time is measured by the regulated flow of liquid into (inflow type) or out from (outflow type) a vessel, and where the amount of liquid can then be measured. Water clocks are some of ...

s, 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 In the practice of Christianity, canonical hours mark the divisions of the day in terms of Fixed prayer times#Christianity, fixed times of prayer at regular intervals. A book of hours, chiefly a breviary, normally contains a version of, or sel ...

of the

Catholic Church The Catholic Church (), also known as the Roman Catholic Church, is the List of Christian denominations by number of members, largest Christian church, with 1.27 to 1.41 billion baptized Catholics Catholic Church by country, worldwid ...

take their names from the Roman clock: the

prime A prime number (or a prime) is a natural number greater than 1 that is not a product of two smaller natural numbers. A natural number greater than 1 that is not prime is called a composite number. For example, 5 is prime because the only ways ...

terce Terce is a canonical hour of the Divine Office. It consists mainly of psalms and is held around 9 a.m. Its name comes from Latin and refers to the third hour of the day after dawn. Along with Prime, Sext, None, and Compline, Terce belongs ...

sext Sext is a canonical hour of the Divine Office in the liturgies of many Christian denominations. It consists mainly of psalms and is held around noon. Its name comes from Latin and refers to the sixth hour of the day after dawn. With Terce, None ...

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 Noon (also known as noontime or midday) is 12 o'clock in the daytime. It is written as 12 noon, 12:00 m. (for '' meridiem'', literally 12:00 midday), 12 p.m. (for ''post meridiem'', literally "after midday"), 12 pm, or 12:00 (using a 24-hour cl ...

'' 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 Noon (also known as noontime or midday) is 12 o'clock in the daytime. It is written as 12 noon, 12:00 m. (for '' meridiem'', literally 12:00 midday), 12 p.m. (for ''post meridiem'', literally "after midday"), 12 pm, or 12:00 (using a 24-hour cloc ...

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 The 12-hour clock is a time convention in which the 24 hours of the day are divided into two periods: a.m. (from Latin , translating to "before midday") and p.m. (from Latin , translating to "after midday"). Each period consists of 12&nb ...

, as opposed to the

24-hour clock The modern 24-hour clock is the convention of timekeeping in which the day runs from midnight to midnight and is divided into 24 hours. This is indicated by the hours (and minutes) passed since midnight, from to , with as an option to indicate ...

References

External links

* {{Time topics History of timekeeping Time measurement systems

Timekeeping Time is the continuous progression of existence that occurs in an apparently irreversible succession from the past, through the present, and into the future. It is a component quantity of various measurements used to sequence events, to compa ...