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How did the Ancient Romans Measure Time? Hours, Days, Nundinae, Kalends, Nones and Ides

Updated on November 9, 2018
SarahLMaguire profile image

Sarah has a PhD in Classical Civilisation from Swansea University. She continues to write on the Ancient World and other topics.

Sundial from the Temple of Apollo, Pompeii
Sundial from the Temple of Apollo, Pompeii

While the modern world has adopted the universal system of a day of twenty-four equal hours and the seven-day week, with roughly four weeks fitted into each of the twelve months, the Romans structured their days and months quite differently.

This article provides a quick and useful guide to how the ancient Romans reckoned time. From looking at the day and its hours and how the Romans told the time, it will go on to describe the important calendrical markers that shaped the Roman month: the Nundinae, the Kalends, the Nones and the Ides and the days Fasti and Nefasti.

The Roman Day: the Horae

The Roman day was divided into twelve equal hours (horae) counted from sunrise to sunset. The first hour after sunrise would be designated the First Hour and the second would be the Second Hour and so on. The last hour of the day would always be the twelfth hour. The hours themselves varied in length, depending on the time of the year, being shorter in the winter and longer in the summer in order to fit them into this twelve hour pattern.

Around the time of the Summer Solstice, Roman hours would be approximately an hour and a quarter of our sixty minute hours. The First Hour would begin at about four thirty am by our reckoning and the Twelfth Hour would end just after seven thirty pm. At the time of the Winter Solstice, hours would last around forty five minutes by our reckoning. The First hour would begin at about seven thirty and the final hour of the day would be around four thirty pm.

The Romans further divided the day into morning (manes) noon (meridies) and afternoon (pomeridianum).

The Hours by Edward Burne Jones
The Hours by Edward Burne Jones

Roman Clocks: Gnomon and Clepsydra

Clockwork was not invented until around the twelfth century CE. The Romans used other forms of technology for telling the time. The two basic means used by the Romans were the sundial or gnomon and the water-clock or clepsydra.

While the gnomon was useful in the garden or in public outdoor spaces, it was of course only effective in sunlight.

The clepsydra worked by allowing water to pour through one glass vessel through a narrow opening into another vessel fitted underneath it, with the second vessel marked off into twelve equal sections corresponding to the hours.

Roman horologia (timepieces) ranged from simple household articles similar to an egg-timer to ornate and elaborate devices that might be on display in public places such as outside temples and courts, or in the homes of the wealthy. The very well off also kept slaves with the specific task of announcing the time to the household.

Some Roman Clepsydra could be very elaborate as this diagram shows. The water pressure would cause the statue to rise so that it indicated the correct hour with a pointer.
Some Roman Clepsydra could be very elaborate as this diagram shows. The water pressure would cause the statue to rise so that it indicated the correct hour with a pointer.

The Nundinae

While we have a seven day week structured around the Christian Sabbath, influenced by the Jewish Shabbat, the Romans had a nine day cycle based around the Nundinae or Market Day.

Beginning on the first of January, the days of the year were divided into blocks of eight, marked A – H on Roman calendars. The eighth day was the Nundinae, Market Day when people came into the city to buy and sell and transact business. The Romans reckoned this as a cycle of nine days because they counted from Nundinae to Nundinae. It was a day particularly associated with the plebeians, the ordinary people of Rome.

The Kalends, Nones and Ides

The Roman month was further divided up and reckoned by the Kalends, the Nones and the Ides.

The Kalends marked the first day of each month, and gave the word Calendar its name.

The Nones occurred on the seventh of March, May, July (or Quinctilis as it was called before the month was renamed in honour of Julius Caesar) and October and on the fifth of the other months.

The Ides always fall eight days after the Nones. Thus the famous Ides of March on which Julius Caesar was assassinated fell on the 15th of March.

The Romans reckoned the days of the month by counting up towards the nearest Kalends, Nones or Ides. If, for example, you wanted to make an arrangement for the 30th of January, you would express the intended date as two days before the Kalends of February.

Detail from the Fasti Praenesti Calendar preserved in the National Museum of Rome.
Detail from the Fasti Praenesti Calendar preserved in the National Museum of Rome.

Days Fasti and Nefasti

Romans further divided their days into those on which courts could be held and business transacted, and those on which such public business was forbidden. Days on which these activities could take place were Fasti and were marked with an F on the Calendar. Days could also be partly Fasti and partly Nefasti so that only part of the day could be devoted to legal or business transactions. Nefasti days were often religious festivals dedicated to the Gods.

On many such days, everyone, including slaves would be exempt from working. Thus, although there was no official Roman weekend or Sabbath, the Romans had several days of rest scattered throughout each month.

The Roman poet Ovid wrote a poem called the Fastii which details the many ancient festivals of the Roman calendar, with their true origins often lost in the mists of time even at the time Ovid was writing in the first century BCE. Sadly, only the first half of the poem, covering the first half of the year, survives.


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