Have you ever wondered why September sounds like it should be the seventh month, even though it appears ninth on today’s calendar?
The same puzzle applies to three other months:
- September sounds like seven but is the ninth month.
- October sounds like eight but is the tenth month.
- November sounds like nine but is the eleventh month.
- December sounds like ten but is the twelfth month.
These names are not mistakes. They are reminders of an older Roman calendar system in which the year originally began in March.
When January and February eventually became part of the beginning of the year, the positions of the later months changed, but their traditional names remained.
To understand why, we need to look back at the history of the Roman calendar.
1. September Was Originally the Seventh Month
The name September comes from the Latin word septem, meaning seven.
In the early Roman calendar tradition, the year began in March rather than January. Under the commonly described ten-month calendar structure, the months followed this order:
| Original position | Month | Meaning of name |
|---|---|---|
| 1 | March | Named after Mars, the Roman god of war |
| 2 | April | Origin of the name is debated |
| 3 | May | Traditionally associated with Maia |
| 4 | June | Traditionally associated with Juno |
| 5 | Quintilis | Fifth |
| 6 | Sextilis | Sixth |
| 7 | September | Seventh |
| 8 | October | Eighth |
| 9 | November | Ninth |
| 10 | December | Tenth |
This explains the numerical pattern.
September was not originally intended to be the ninth month. It occupied the seventh position in a calendar that began in March.
The Latin roots of the final four names preserve that older arrangement.
2. Why Did the Roman Year Begin in March?
March was an important month in ancient Roman life.
Its name comes from Mars, the Roman god associated with war. In early Roman society, military campaigns and agricultural activities were closely connected to the changing seasons.
Spring marked a practical beginning for many activities. As the weather improved, it became easier to travel, prepare fields and organise military campaigns.
This helps explain why March held an important position in the early Roman calendar tradition.
However, the historical development of the Roman calendar was not as simple as one perfectly documented system being used unchanged for centuries. The earliest calendar arrangements are partly reconstructed from later Roman accounts.
The familiar ten-month calendar is a traditional explanation of Rome’s early calendar history, not a complete modern record of how every date was counted.
3. Where Did January and February Come From?
The early Roman calendar tradition is associated with a ten-month year that did not account for the full solar year.
The months covered approximately 304 days, leaving a period of winter outside the regular monthly structure in traditional accounts.
January and February were later added to bring the calendar closer to the seasonal and lunar cycles.
These months are traditionally associated with the Roman king Numa Pompilius, although the details of the early reform are uncertain.
January takes its name from Janus, the Roman god associated with beginnings, transitions and doorways.
February comes from Februa, a term associated with Roman purification rituals.
With these two months included, the Roman calendar had 12 months.
But adding January and February did not immediately make the modern calendar system identical to the one we use today.
4. How Did September Move From Seventh to Ninth?
Once January and February were placed before March, the numerical positions of the later months shifted.
September moved from seventh to ninth.
October moved from eighth to tenth.
November moved from ninth to eleventh.
December moved from tenth to twelfth.
The important detail is that the names did not change along with their positions.
| Month | Meaning of Latin root | Original position | Modern position |
|---|---|---|---|
| September | Seven | 7th | 9th |
| October | Eight | 8th | 10th |
| November | Nine | 9th | 11th |
| December | Ten | 10th | 12th |
This is why the modern calendar appears to contain a numbering contradiction.
The names reflect an older arrangement, while the current month order reflects later calendar reforms.
5. Why Were the Month Names Never Changed?
When the Roman calendar developed, its traditional month names became deeply established in everyday life.
Changing them would have required more than correcting a numbering mismatch.
People used these names in:
- Government records.
- Religious ceremonies.
- Agricultural activities.
- Public announcements.
- Commercial transactions.
- Historical documents.
The names also became part of the Roman administrative and cultural system.
As Roman influence spread, the Latin month names influenced the calendars and languages of many European societies.
Over time, the names continued to be used even as calendar systems changed.
There was little practical reason to rename September, October, November and December simply because their numerical meanings no longer matched their modern positions.
Today, their historical roots are still visible in English and many other languages.
6. How Did the Julian Calendar Affect the Month Names?
Another important development in calendar history occurred during the rule of Julius Caesar.
The Roman calendar had become increasingly difficult to manage because its relationship with the seasons was not maintained consistently.
In 46 BCE, Julius Caesar introduced a major calendar reform, implemented from 45 BCE.
This system became known as the Julian calendar.
It established a regular year of 365 days, with an additional day every four years. Its average year length was therefore 365.25 days.
The reform improved the organisation of the Roman calendar and helped bring it closer to the solar year.
However, it did not rename September or move the month names back to their original numerical positions.
The familiar month names continued to be used.
What happened to Quintilis and Sextilis?
Two other Roman month names did change.
The month Quintilis, originally the fifth month in the older March-based arrangement, was renamed July in honour of Julius Caesar.
Sextilis was later renamed August in honour of Emperor Augustus.
This is another reason why modern month names preserve different parts of Roman history.
7. Did the Gregorian Calendar Change September’s Position?
No.
The Gregorian calendar, introduced by Pope Gregory XIII in 1582, corrected the way leap years were calculated to improve the calendar’s alignment with the solar year.
It retained the existing 12-month structure and the established month names.
Under the Gregorian system:
- September remains the ninth month.
- October remains the tenth month.
- November remains the eleventh month.
- December remains the twelfth month.
The reform changed the leap-year rules, not the historical naming system.
Today, the Gregorian calendar is the most widely used civil calendar internationally.
8. Why Do October, November and December Also Have Number Meanings?
The same historical explanation applies to all four months.
Their names come from Latin numerical words.
| Month | Latin word | Meaning |
|---|---|---|
| September | Septem | Seven |
| October | Octo | Eight |
| November | Novem | Nine |
| December | Decem | Ten |
The number-based names make sense when viewed through the older March-based calendar.
But they seem unusual when compared with the modern January-to-December order.
Interestingly, the word octopus also contains the Latin-derived root associated with eight, while decimal comes from the Latin word for ten.
These connections show how ancient numerical roots continue to appear in modern vocabulary.
9. A Simple Way to Remember the Historical Order
If you find it difficult to remember why September is the ninth month, use this simple pattern:
Old calendar order:
March → April → May → June → July → August → September → October → November → December
Modern calendar order:
January → February → March → April → May → June → July → August → September → October → November → December
Notice what happened?
January and February appear before March in the modern calendar. The final four numerical month names therefore appear two positions later than their original meanings suggest.
This is the easiest way to remember the mystery:
September was seventh, October was eighth, November was ninth and December was tenth in the traditional March-based arrangement.
10. What Does This Tell Us About the History of Calendars?
The September mystery reveals something interesting about how calendars develop.
A calendar is not simply a list of months. It is a system shaped by astronomy, agriculture, religion, government and social habits.
As societies changed, their calendars were adjusted to suit new needs.
Sometimes the number of months changed. Sometimes the beginning of the year shifted. Sometimes leap-year rules were revised.
But familiar names and traditions often survived these changes.
That is why a modern calendar can contain names that reflect an arrangement used more than two thousand years ago.
September is a small example of how history remains hidden in everyday things we rarely question.
Frequently Asked Questions
Why is September called September if it is the ninth month?
September comes from the Latin word septem, meaning seven. It was originally the seventh month in the traditional early Roman calendar, which began in March. When January and February were placed before March, September became the ninth month, but its name remained unchanged.
What did September originally mean?
September originally meant the seventh month. Its name is derived from the Latin numerical word septem.
Why does October mean eight but come tenth?
October comes from the Latin word octo, meaning eight. In the older March-based Roman calendar, October was the eighth month. Its position shifted to tenth after January and February were placed before March.
Why does November mean nine?
November comes from the Latin word novem, meaning nine. It was traditionally the ninth month in the early Roman calendar arrangement.
Why does December mean ten?
December comes from the Latin word decem, meaning ten. It originally occupied the tenth position in the traditional March-based calendar.
Did the Romans originally have only ten months?
Traditional accounts describe an early Roman calendar with ten named months beginning in March, covering approximately 304 days. January and February were later added. The details of the earliest Roman calendar are historically uncertain and are partly based on later Roman traditions.
Who added January and February?
Roman tradition credits Numa Pompilius with introducing January and February. However, the exact history and timing of the early calendar reforms are not fully certain.
Did Julius Caesar make September the ninth month?
Julius Caesar’s calendar reform established the Julian calendar, but it did not create the original shift in September’s position. The placement of January and February before March had already developed in the Roman calendar system.
Did the Gregorian calendar rename the months?
No. The Gregorian calendar reform of 1582 adjusted leap-year rules and retained the established 12-month structure and month names.
Final Thoughts
September is the ninth month today, but its name still remembers a time when the Roman year began in March.
The same story explains October, November and December. Their Latin roots mean eight, nine and ten, even though they now occupy the tenth, eleventh and twelfth positions.
The next time you look at a calendar, remember that these names are not mistakes. They are historical reminders of how the Roman calendar evolved over many centuries.
Sometimes, the simplest things on a calendar carry the longest stories.