Time & Calendar Mores

  The Calendar of Ancient Rome  

To calculate dates as one did in ancient Rome, use the following formula:

Kalendae The 1st of each month (Kalends in English).
Nonae The 5th of all but 4 months. (Nones in English)
The 7th in March, May, July and October
Idus The13 th of all but 4 months (Ides in English)
The 15th in March, May, July and October

Any date that does not fall on the Kalends, Nones or Ides is calculated by counting the number of days between that day and the nearest of the three target days.

The months are considered adjectives which agree with the target days of :
kalendae (f.-1st declension)
nonae (f.-1st declension)
idus(f.-4th declension)


Sept 5 - Nonae Septembres

Sept 4 - Pridie Nonas Septembres

The day before one of the target days is called
pridie nonas, pridie idus or pridie kalendas.

Sept. 2 - ante diem iv Nones Septembres

One needs to count : Sept. 2 + Sept. 3 + Sept. 4 + Sept. 5 = 4 days.
You therefore write that Sept. 2 comes 4 days before Sept. 5, counting both the 2nd and the 5th in your calculation. Use the term, before the day-ante diem- to indicate the count.

Practice with some favorite dates such as your birthday, Thanksgiving, Halloween etc.
Refer to your classroom Roman calendar to check your calculations

To use dates in context:

Ablative of Time -indicates on a given target date Nonis Februariis = on Feb. 5
  Kalendis Aprilibus = on April 1
  Idibus Martiis = on March 15

To express the day before a target date: Pridie + accusative case

To express other dates: ante diem ( # of days prior to target date, including the target date) then the target date and month in the accusative case: ante diem v kalendas septembres = August 27.
Count the 27th and the 1st in your calculations.

KET students: Try this exercise : Know that day?
( Doleo! This activity is restricted to registered students because it is linked to our grading program. You might try making up your own list of dates and quizzing others in your class)


Calendars in ancient days were often carved in stone

View calendar image

Days ( Dies )

Romans calculated a week as a period of nine days. It was called Nundinae.
Every ninth day was a market day.

The seven-day period was not officially adopted by Constantine until 321 A.D. Notice the names of the days and the connections these names have to both the names of days in English and other languages.


Notice that one says day of sun, day of moon, day of Mars etc.

Special Days:

Fasti days when legal action is permitted ( contracts, weddings, law suits etc.)
Nefasti no legal action or public voting could take place on these days.
Dies Comitiales days when committees of citizens could vote on political or criminal matters
Feriae Holidays - games, plays, banquets usually in honor of gods; no public business was allowed See your Feriae booklet for a description of the feriae.

A Brief History of the Calendar.

In ancient Rome, the Pontifex Minor observed the small crescent of the new moon , declared it to be a new moon and thus a new month. Romans referred to the first day of each new month as the Kalendae (Calendae) from the Latin word calare which means to call out or announce with seriousness of purpose. A new moon was sighted usually after 29 or 30 days. If clouds obscured the moon on day 30, the new moon would be declared to be on the 31st day.

The original Roman calendar was divided into ten months of irregular lengths. Numa Pompilius is reputed to have added the additional two months but maintained the beginning of the year as March 15. By the time of Julius Caesar the Numa calendar was three months ahead of the seasons. Winter started in September. Caesar used the Egyptian calendar as a base and establish a new calendar drawn (the Julian calendar), with 12 months of 31 or 30 days, except February, which had 29 days. Every fourth year, February had 30 days, to realign the calendar.

It is generally accepted that Caesar established January as the beginning of the year but there are some who claim it was Numa and some Gregory.

The origin of the names for April through June are uncertain. Some ancient authors claimed that the name Aprilis was derived from Aphrodite. Others say that April was derived from aperire (to open), and claim that names of months we now call April, May and June refer to growth stages of crops or cattle.

Learn more about the History of the Calendar on these sites:

Roman Phrase:
Ad Kalendas Graecas =
Till hell freezes over
The Greeks did not use the Kalends

How the Romans Measured Time

One measured time in ancient days by the length of daylight. As the earth makes its way around the sun, the number of daylight hours change. For the Romans who divided the day into equal parts of daytime and nighttime, the length of those parts varied with the amount of light. Unlike our hour of a constant 60 minutes, the Roman hour could be anywhere from 40 minutes to 80 minutes. Consider Alaska where one can easily experience darkness for 22 hours with daylight of 2 hours. The Romans would have calculated the day then at one of twelve 10 minutes hours and the night of twelve 110 minute hours. The Romans never experienced such extremes of course but this example serves to clarify the idea of the division of hours or watches.

Time was measured with sundials, waterclocks and sand glasses.

The History of Clocks

Early Clocks



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