Every month on your calendar carries a name handed down from ancient Rome, and most of them are over 2,000 years old. The origins break into three neat categories: gods and goddesses, Roman leaders, and plain Latin numbers that no longer match their position in the year. That last group is the one that surprises most people.
Rome’s Original Ten-Month Calendar
The earliest Roman calendar had only ten months, starting in March and ending in December. Winter was essentially uncounted time, a dead stretch between the end of one agricultural year and the start of the next. This ten-month structure is the key to understanding why September through December sound like they should be the seventh through tenth months: they originally were.
Around the 7th century BC, Numa Pompilius, the second king of Rome, added two new months to fill that winter gap. He took fifty days from the existing calendar and pulled one day from each of the thirty-day months to create January and February, both initially 28 days long. These two months were tacked onto the end of the year at first, but eventually January migrated to the front, becoming the start of the new year. That shift pushed every numbered month two slots forward, and no one ever bothered to rename them.
January Through March: Gods of War and New Beginnings
January is named for Janus, the Roman god of beginnings, transitions, and doorways. He’s traditionally depicted with two faces, one looking into the past and one into the future, which made him a fitting symbol for the turn of the year.
February comes from the Latin word februa, meaning “to cleanse.” The Romans held a purification festival called Februalia during this period, a time of ritual washing and atonement before the new agricultural season.
March is named for Mars, the Roman god of war. As the original first month of the Roman calendar, March marked the time when weather improved enough to resume military campaigns. It was a month of action, not reflection.
April Through June: Spring and Its Contested Origins
April has one of the more debated etymologies. The traditional explanation connects it to the Latin verb aperire, meaning “to open,” as in flowers opening in spring. But many scholars consider this folk etymology. A more likely origin traces the name through Etruscan to the Greek goddess Aphrodite. The Etruscans, who heavily influenced early Roman culture, borrowed the Greek name and passed it along. The Romans themselves associated April with Venus, their version of Aphrodite, which supports this connection.
May takes its name from Maia, a Greek goddess associated with growth and fertility. The choice fit the season: crops were growing, and the landscape was turning green.
June honors Juno, the Roman goddess of marriage and childbirth and wife of Jupiter, king of the gods. This association is one reason June weddings became a longstanding tradition.
July and August: Political Rebranding
These two months originally had numerical names. July was Quintilis (the fifth month), and August was Sextilis (the sixth). Both were renamed to honor Roman rulers.
July was renamed after Julius Caesar’s assassination in 44 BC. The Roman Senate changed Quintilis to Julius because it was Caesar’s birth month. Caesar had also been the driving force behind the major calendar reform that replaced the old, error-prone Roman calendar with the more accurate Julian calendar in 46 BC, so the honor carried a practical justification too.
August followed the same pattern. The Senate renamed Sextilis to Augustus in honor of Emperor Augustus, Caesar’s adopted heir and Rome’s first emperor. The gesture was partly flattery and partly acknowledgment of Augustus’s own calendar corrections.
There were later attempts to rename other months after emperors. Nero, Domitian, and Commodus all tried. None of those names stuck, which is why September through December still carry their old numerical labels instead of imperial ones.
September Through December: Numbers in the Wrong Spot
This is the group that makes people do a double take once they notice the pattern.
- September comes from septem, Latin for seven. It’s now the ninth month.
- October comes from octo, Latin for eight. It’s now the tenth month.
- November comes from novem, Latin for nine. It’s now the eleventh month.
- December comes from decem, Latin for ten. It’s now the twelfth month.
Each one is exactly two positions off from its name, the direct result of January and February being inserted before March. By the time this mismatch was obvious, the names were already too deeply embedded in Roman life to change. Two thousand years later, they still are.
Why the Names Never Changed
The biggest calendar overhaul since Julius Caesar came in 1582, when Pope Gregory XIII introduced the Gregorian calendar. But that reform only fixed a mathematical problem: the Julian calendar had been gaining about one day every 128 years, slowly pushing the dates of the equinoxes out of alignment. Gregory’s fix was to skip 10 days (Thursday, October 4, 1582, was followed by Friday, October 15) and adjust the leap year rules. The month names and their lengths stayed exactly the same.
Other cultures did use different names. The Anglo-Saxons, for example, had their own calendar where months reflected local climate and customs. February was Sol-monaþ (mud month), April was Eostur-monaþ (the root of “Easter”), and November was Blot-monaþ (sacrifice month, when livestock were slaughtered before winter). As Roman influence and Christianity spread across Europe, these local names gradually fell out of use and the Latin versions became standard.
The French Revolution actually tried to replace the Roman month names entirely in 1793, introducing poetic alternatives based on weather and agriculture. That system lasted about 12 years before Napoleon scrapped it and restored the traditional calendar. It remains the most serious modern attempt to rename the months, and its failure says something about how resistant calendar conventions are to change. The Roman names, imperfect as they are, have outlasted every empire that tried to replace them.