Origin of the names of the Months

THE ROMAN CALENDAR

The Roman calendar is the ancestor of our modern calendar. Some of its features are still in use today.

The Roman calendar is the time reckoning system used in ancient Rome. However, because the calendar was reformed and adjusted countless times over the centuries, the term essentially denotes a series of evolving calendar systems, whose structures are partly unknown and vary quite a bit.

Here, we focus mainly on the calendar used in the Roman Republic (509-27 BCE). Also known as the Republican calendar, it is the earliest calendar system from Rome for which we have historical evidence. It was used until 45 BCE, when it was replaced by the Julian calendar.

BASED ON ANCIENT LUNAR CALENDARS

The Republican calendar was derived from a line of older calendar systems whose exact design is largely unknown. It is believed that the original Roman calendar was a lunar calendar that followed the phases of the Moon. This basic structure was preserved through the centuries, which is the reason why we use months today.

ONLY 10 MONTHS AT FIRST

According to tradition, Romulus, the legendary first king of Rome, oversaw an overhaul of the Roman calendar system around 738 BCE. The resulting calendar, whose structure borrowed heavily from the ancient Greek calendar system, had only 10 months, with March (Martius) being the first month of the year. The winter season was not assigned to any month, so the year only lasted 304 days, with 61 days unaccounted for in the winter.

REPUBLICAN CALENDAR ADDS JANUARY AND FEBRUARY

Following another calendar reform, which later Roman writers attributed to Romulus' successor, Numa Pompilius, the Republican calendar was instituted. To account for the days of winter between the years, two additional months were introduced: Ianuarius and Februarius.

This meant that some of the month names no longer agreed with their position in the calendar. For example, September means “the 7th month,” but it was now the 9th month of the year — an inconsistency that was preserved and is still part of the Gregorian calendar we use today.

A common year was now divided into 12 months of different lengths: 4 “full” months with 31 days, 7 “hollow” months with 29 days, and 1 month with 28 days.

Only a few names of the month were derived from Roman deities. Most simply came from the numbers of the months or in two cases in honour of Roman emperors. 

Named after the Roman god of beginnings and endings Ianus (the month Ianuarius).  The name comes either from the old Italian god Februus or else from februa, signifying the festivals of purification celebrated in Rome during this month.  This is the first month of the Roman year. It is named after the Roman god of war, Mars.  Called Aprilis, from aperire, "to open". Possible because it is the month in which the buds begin to open.

The third month of the Roman calendar. The name probably comes from Maiesta, the Roman goddess of honour and reverence. 

The fourth month was named in honour of Juno. However, the name might also come from iuniores (young men; juniors) as opposed to maiores (grown men; majors) for May, the two months being dedicated to young and old men. 

It was the month in which Gaius Iulius Caesar was born, and named Iulius in his honour in 44 BCE, the year of his assassination. Also called Quintilis (fifth month).

Originally this month was called Sextilis (from sextus, "six"), but the name was later changed in honour of the first of the Roman emperors, Augustus (because several fortunate events of his life occurred during this month). 

The name comes from septem, "seven". 

The name comes from octo, "eight".

The name comes from novem, "nine". 

The name comes from decem, "ten".

Months in the Republican Calendar (Common Year)

MONTH NAMES NUMBER OF DAYS

Ianuarius 29

Februarius 28

Martius 31

Aprilis 29

Maius 31

Iunius 29

Quintilis 31

Sextilis 29

September 29

October 31

November 29

December 29

Months in the Gregorian Calendar (Common Year)

MONTH NAMES NUMBER OF DAYS

January 31

February 28/29

March 31

April 30

May 31

June 30

July 31

August 31

September 30

October 31

November 30

December 31