Names of the Months

Where we get the twelve English names for the months of the year.

Bonnie Mills, Writing for
4-minute read
Episode #553


As with many words in English, the twelve words we use for the twelve months come from Latin. Strangely enough, though, the ancient Romans had only ten months for a while. Over the centuries, other calendars have been introduced, evolving into the one we use today.

The Ten Roman Months

Centuries ago, around 753 BC, it’s believed that Romulus, the first king of Rome, invented the original, pre-Julian, Roman calendar, which was probably a lunar calendar, meaning it was based on the cycles of the moon. This calendar had ten months covering 304 days. The months were named Martius, Aprilis, Maius, Iunius, Quintilis, Sextilis, September, October, November, and December. (1) 

The first four Roman months sound less familiar than the later ones. The names of Roman gods and goddesses figure into three of the four names: Martius was named for Mars, the god of war; (2) Maius comes from Maia, the goddess who “oversaw the growth of plants”; (3) and Iunius comes from Juno, “patroness of marriage and the well-being of women.” (3) Aprilis is the odd one out, likely coming from aperire, the Latin word for “open.” Aprilis was so named “because it is the month in which the buds begin to open.” (2) Incidentally, another English word that comes from aperire is aperture, which refers to a small opening such as a hole or a gap. (4) 

The names of the last six months in the Roman calendar—Quintilis through December—seem strictly number based. Quintilis starts with quint, meaning “five,” as in the word quintuplets, referring to five babies born at once. Likewise, Sextilis, relates to the number six, as in the word sextuplets. You won’t be surprised to learn that the months September through December originate from the Latin septem, octo, novem, and decem, the numbers seven through ten, respectively. (2)

January and February

To recap, Martius became March, Aprilis turned into April, Maius is now May, and Iunius became June. September through December are pretty clear. Together, those make eight of the twelve month names, so there are four left to discuss. Up next are January and February; we’ll talk more about Quintilis and Sextilis, now July and August, in a minute.

According to timeanddate.com, the 304-day Roman calendar was flawed because “it didn’t align with the seasons,” and about 61 days were missing during the winter. (1) To solve this, around 700 BC, King Numa Pompilius added 50 or 51 days to the calendar, adding two months to the beginning of the year. These were called Januarius and Februarius, our January and February. Januarius comes from Janus, the Roman god who protected gates and doorways, and the word Februarius originates with Februalia, a Roman “festival of purification and atonement.” (3) If you have ever wondered why there is a silent R in the middle of the word February, you have the Latin februa, meaning “to cleanse,” to thank for this spelling difficulty. (3) 

The Julian Calendar, and July and August

Despite the addition of two months, the calendar still had problems. (1) After the Romans made various failed attempts to align the calendar with the seasons, it was decided to add what was called the “intercalary month.” The high priest of the College of Pontiffs in ancient Rome (otherwise known as the pontifex maximus) got to control when to insert this extra month, and this became a problem because “a pontifex maximus could control the length of the year depending on (his) political agenda.” (1) 

Julius Caesar, who lived from 100 BC to 44 BC, began developing what was known as the Julian Calendar in 46 BC, and he abolished the intercalary month. (3) The Julian Calendar was completed during the reign of Caesar’s successor and grandnephew, Augustus, (1) who lived from 63 BC to 13 AD. The names Quintilis and Sextilis were changed to July and August, respectively, in honor of these two leaders: Julius Caesar and his grandnephew Augustus. (3)

The Gregorian Calendar

The Julian Calendar was in effect for centuries, but this is not our calendar today. We use the Gregorian Calendar, named after Pope Gregory XIII, who issued a papal bull about it in 1582. A papal bull is a letter or announcement from the pope to the Catholic world. The pope felt the Julian Calendar had to be replaced because “it did not properly reflect the actual time it takes the Earth to circle once around the Sun, known as a tropical year.” (5) The Julian Calendar had “miscalculated the length of the solar year,” and as a result the calendar didn’t coincide with the seasons, especially Easter, which the church wanted to schedule relative to the spring equinox. (6) The solution was to chop out some days—quite a few, in fact. It took more than 300 years for all countries to adopt the calendar, and the longer they waited, the more days they had to cut. For example, when Britain and its American colonies switched to the Gregorian Calendar in 1752, they deleted 11 days,(7) whereas Turkey, the last country to make the official switch in 1927, had to delete 13 days. (8)

The Calendar Today

The calendar we use today is quite accurate but not perfect. Experts calculate that come year 4909 on the Gregorian calendar, we’ll be off by a day again. (8) That’s a long way off, so for now just make sure to put in that silent R when you are spelling the word February.

That segment was written by Bonnie Mills, author of The Curious Case of the Misplaced Modifier.


1. timeanddate.com. “The Roman Calendar.” https://www.timeanddate.com/calendar/roman-calendar.html. Accessed January 15, 2017.

2. Encyclopedia Mythica. “Origin of the names of the months.” http://www.pantheon.org/miscellaneous/origin_months.html. Accessed January 15, 2017.

3. The Old Farmer’s Almanac. “Origin of Month Names.” http://www.almanac.com/content/origin-month-names. Accessed January 15, 2017.

4. Dictionary.com. “Aperture.” http://www.dictionary.com/browse/aperture?s=t. Accessed January 15, 2017.

5. timeanddate.com. “Change From Julian to Gregorian Calendar.” https://www.timeanddate.com/calendar/julian-gregorian-switch.html. Accessed January 15, 2017.

6. History.com. “6 Things You May Not Know About The Gregorian Calendar.” http://www.history.com/news/6-things-you-may-not-know-about-the-gregorian-calendar. Accessed January 15, 2017.

7. “1752 Calendar Change.” http://libguides.ctstatelibrary.org/hg/colonialresearch/calendar. Accessed January 23, 2017.

8. timeanddate.com. “Change From Julian to Gregorian Calendar.” https://www.timeanddate.com/calendar/julian-gregorian-switch.html. Accessed January 15, 2017.

Image courtesy of Shutterstock.

About the Author

Bonnie Mills, Writing for Grammar Girl

Bonnie Mills has been a copyeditor since 1996.