Roman Time & Calendar

Roman Days of the Week

Dies Nundinarum

Romans calculated a week as a period of nine days. It was called Nundinae. Every ninth day was a market day. They borrowed this formula from the Etruscan Market Week.

The seven day week became common around the first century A.D. Augustus used the seven day calendar and the ancient market calendar simultaneously. However, the seven-day period was not officially adopted until emperor Constantine in 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 et cetera:

Look at the similarities of the names of the week in Romance languages!

Special Days:

A Brief History of the Calendar

The first Roman calendar, based on a lunar cycle, is said to have been introduced by Romulus. 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: Martius, Aprilis, Maius, Iunius, Quintilis, Sextilis, September, October, November, December. Numa Pompilius is reputed to have added the additional two months circa 750 BCE but maintained the beginning of the year as March 15. The Roman Senate decided to move Ianuarius to begin the year, in honor of the god of beginnings, Janus. This was about 153 BCE.

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.

Some claim that Caesar, in 45 BCE, established January as the beginning of the year. We do know that Caesar revised the calendar to a solar calendar design he had borrowed from Egypt and the astronomer Sosogenes. Caesar's solar year was 365 days and 6 hours, which was 11 min. and 45 seconds too long. So, Pope Gregory XIII introduced a revised calendar in 1582.

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. Quintilis was renamed in honor of Julius Caesar (July) who had been born on the 12th of that month - a.d.ii ides iulias. Sextilis was renamed Augustus in honor of Octavianus Augustus who died on 19 August 14 CE : a.d. xviii kal. sept.

Interesting facts of today's calendar:

• A lunar calendar is still used in Jewish religious calculations.
• The dates of all moveable Christian feast days depend on Easter which is still calculated according to the lunar calendar thus Easter is celebrated on the first sunday after the 1st full moon on or after the Vernal Equinox (March 12).
• The Julian calendar is still used in Easter Orthodox churches.

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

• History of the calendar
• Ancient Calendars
• Julian Calendar
• Gregorian Calendar
• Plutarch's comments re calendars

J.Jahnige, 2005