This page cannot be viewed in frames

Go to page

If you have found a spelling error, please, notify us by selecting that text and pressing Ctrl+Enter.

Roman dating and counting of days

This post is also available in: Polish (polski)

The month of February is depicted on a Roman mosaic from the 1st half of  the 3rd century CE. It is located in the Archaeological Museum of Sousse  (Tunisia).
The month of February is depicted on a Roman mosaic from the 1st half of the 3rd century CE. It is located in the Archaeological Museum of Sousse (Tunisia).

As it turns out, the Roman way of counting and determining specific days in a month was different from what we use now. Ancient Romans used the following terms: calends, nones, ides.

In the beginning, however, it is worth mentioning some important matters regarding the Roman calendar. In Rome of the royal period, there were 304 days, which were divided into 10 months. The beginning of the year began on March 1 – the time of the spring equinox. During the reign of the second king, Numa Pompilius, there was introduced a change in the calendar – in total there were 355 days. The division into 12 months was also formed, where Ianuarius was the first month in the year:

  • Ianuarius – the name comes from the god Janus.
  • Februarius – we don’t know exactly where the name comes from.
  • Martius – the name comes from the god Mars.
  • April fools – we do not know exactly where the name comes from.
  • Maius – the name comes from the goddess Maia.
  • Iunius – the name comes from the goddess Junona.
  • Quintilis – the name comes from the number “five” (quinque), which is due to the fact that the original Roman calendar began in March (the change occurred after Pompilii Numbers).
  • Sextilis – the name comes from the number “six” (sex).
  • September – the name comes from the number “seven” (septem).
  • October – the name derives from the number “eight” (octo).
  • November – the name derives from the number “nine” (novem).
  • December – the name is derived from the number “ten” (decem).

In 44 BCE the month of Quintilis was given a new name – Iulius, in honour of Julius Caesar (hence the English name of the month “July”). In 8 BCE in honour of Octavian Augustus month Sextilis was changed to Augustus (the modern English name “August”).

Martius, Maius, Iulius, October had 31 days. Februarius – 28 days. All others had 29 days. The solar calendar totalled 355 days. Deficiencies in days, relative to the movement of the sun, were supplemented by Pontifex Maximus with mercedonius (also known as intercalaris or mensis intercalaris). An additional month, according to tradition, was introduced by Numa Pompilius. This month was placed between February 23 and 24 and had 22 days. Initially, it was added every 2 years, but in practice, Pontifex Maximus used it from 191 BCE. at its own discretion (reform of consul Glabrio). For example, between 59 and 46 BCE, this month was not used at all, once in other years, it was used too often, what caused a lot of chaos in the calendar – including the fact that seasons did not coincide with the months. Its use was usually purely political because in this way it was possible to extend the duration of the office or speed up the end of the office.

With the reform of the calendar under Julius Caesar (46 BCE), the month mercedonius was abolished. Julius Caesar, with the help of his astronomer Sosigenes of Alexandria, calculated that each year consists of 365,25 days. He determined the number of days for individual months (30 or 31 or 29 for Februarius) and made February a leap year every four years. The change, however, was not to add one day to February, as is done today, but to repeat it the same day. So every four years, every Roman lived the same day twice. It was set for February 24 (called bissextus, “twice sixth”, as this day was 6 days before calends of March). Moreover, the number of days in Augustus was increased to 31, once one day was taken from Februarius (the number decreased from 29 to 28).

The Roman calendar used terms to specify specific days of the month. distinguished:

  • Calends – the first day of the month.
  • Nones – day 5 (for a month with 29 days) or 7 (for a month with 31 days). The name comes from the word “ninth” (nonus).
  • Ides – day 13 (for a month with 29 days) or 15 (for a month with 31 days).

How did the Romans mark a given day of the month? They used calends, nones and ides for this. To determine the exact day, days were counted inclusive from those specified dates. And so for October:

  • October 1 – calends of October (Kalendis Octobribus)
  • October 2 – sixth day before October (ante diem VI Nonas Octobres)
  • October 7 – nones of October (Nonis Octobribus)
  • October 8 – the eighth day before the ides of October (ante diem VIII Idus Octobris)
  • October 14 – the day before the ides of October (pridie Idus Octobris)
  • October 16 – the seventeenth day before the calends of November (ante diem XVII Kalendis Novembris)
  • William Matthew O'Neil, Time and the Calendars
  • Roman Dates, "latintutorial"
  • Photo: © Ad Meskens / Wikimedia Commons

IMPERIUM ROMANUM needs your support!

If you like the content that I collect on the website and that I share on social media channels I will be grateful for the support. Even the smallest amounts will allow me to pay for further corrections, improvements on the site and pay the server.



Find out more!

Check your curiosity and learn something new about the ancient world of the Romans. By clicking on the link below, you will be redirected to a random entry.

Random curiosity

Random curiosity

Discover secrets of ancient Rome!

If you want to be up to date with newest articles on website and discoveries from the world of ancient Rome, subscribe to the newsletter, which is sent each Saturday.

Subscribe to newsletter!

Subscribe to newsletter

Spelling error report

The following text will be sent to our editors: