Roman Timekeeping
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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 advent of the
sundial A sundial is a horological device that tells the time of day (referred to as civil time in modern usage) when direct sunlight shines by the apparent position of the Sun in the sky. In the narrowest sense of the word, it consists of a flat ...
circa 263 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 Daytime as observed on Earth is the period of the day during which a given location experiences natural illumination from direct sunlight. Daytime occurs when the Sun appears above the local horizon, that is, anywhere on the globe's hemis ...
, 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 vice versa 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 north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the e ...
latitude, one hour was about 45 minutes at the
winter solstice The winter solstice, also called the hibernal solstice, occurs when either of Earth's poles reaches its maximum tilt away from the Sun. This happens twice yearly, once in each hemisphere ( Northern and Southern). For that hemisphere, the winte ...
, and 75 minutes at
summer solstice The summer solstice, also called the estival solstice or midsummer, 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). For that hemisphere, the summer ...
. The Romans understood that as well as varying by season, the length of daytime depended on
latitude In geography, latitude is a 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 the south pole to 90° at the north pol ...
.


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. The
sundial A sundial is a horological device that tells the time of day (referred to as civil time in modern usage) when direct sunlight shines by the apparent position of the Sun in the sky. In the narrowest sense of the word, it consists of a flat ...
was imported from
Sicily (man) it, Siciliana (woman) , population_note = , population_blank1_title = , population_blank1 = , demographics_type1 = Ethnicity , demographics1_footnotes = , demographi ...
in 263 BC and they were set up in public places. Sundials were used 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 is then measured. Water clocks are one of the oldest time-m ...
s. The disadvantage of sundials, or shadow clocks, was that they worked only in sunshine and had to be recalibrated depending on the latitude and season.


Legacy

*The Roman day starting at dawn survives today in the Spanish word ''
siesta A ''siesta'' (from Spanish, pronounced and meaning "nap") is a short nap taken in the early afternoon, often after the midday meal. Such a period of sleep is a common tradition in some countries, particularly those in warm-weather zones. The ...
'', 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 times of prayer at regular intervals. A book of hours, chiefly a breviary, normally contains a version of, or selection from, such prayers. In ...
of the
Catholic Church The Catholic Church, also known as the Roman Catholic Church, is the largest Christian church, with 1.3 billion baptized Catholics worldwide . It is among the world's oldest and largest international institutions, and has played a ...
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. With Sext, None and Compline it belongs to the so-called "Litt ...
,
sext Sext, or Sixth Hour, is a canonical hour of the Divine Office of almost all the traditional Christian liturgies. 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. ...
and
none None may refer to: *Zero, the mathematical concept of the quantity "none" *Empty set, the mathematical concept of the collection of things represented by "none" *''none'', an indefinite pronoun in the English language Music * ''None'' (Meshuggah E ...
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 (or midday) is 12 o'clock in the daytime. It is written as 12 noon, 12:00 m. (for meridiem, literally 12:00 noon), 12 p.m. (for post meridiem, literally "after noon"), 12 pm, or 12:00 (using a 24-hour clock) or 1200 (military time). Solar ...
'' 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 (or midday) is 12 12-hour clock, o'clock in the daytime. It is written as 12 noon, 12:00 m. (for 12-hour clock, meridiem, literally 12:00 noon), 12 p.m. (for 12-hour clock, post meridiem, literally "after noon"), 12 pm, or 12:00 (using a 24 ...
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"). For different opinions on represent ...
, as opposed to the
24-hour clock The modern 24-hour clock, popularly referred to in the United States as military time, 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) pas ...
.


See also

*
Ancient Greek calendars Various ancient Greek calendars began in most states of ancient Greece between Autumn and Winter except for the Attic calendar, which began in Summer. The Greeks, as early as the time of Homer, appear to have been familiar with the division of th ...
*
Egyptian calendar The ancient Egyptian calendar – a civil calendar – was a solar calendar with a 365-day year. The year consisted of three seasons of 120 days each, plus an intercalary month of five epagomenal days treated as outside of the year proper. Eac ...
*
Roman calendar The Roman calendar was the calendar used by the Roman Kingdom and Roman Republic. The term often includes the Julian calendar established by the reforms of the Roman dictator, dictator Julius Caesar and Roman emperor, emperor Augustus in the ...
*
Relative hour Relative hour (Hebrew singular: / ; plural: / ), sometimes called halachic hour, seasonal hour and variable hour, is a term used in rabbinic Jewish law that assigns 12 hours to each day and 12 hours to each night, all throughout the year. A rela ...


References

{{Commons category, Ancient Roman time keeping Timekeeping Time measurement systems Ancient Roman units of measurement