Why Months Have the Names They Do
Month names come from a mix of Roman deities, numbers, Latin words, and later calendar reforms that aligned the calendar with the solar year. The earliest Roman calendar began with Martius (March) and had ten months; January and February were added later, and July and August were renamed to honor Julius and Augustus Caesar. Across languages, month names preserve these origins in calendars shaped by astronomy, politics, and cultural exchange. This guide explains each month’s etymology, historical shifts, and why the Gregorian calendar now anchors civil systems worldwide.
Roman Calendar Origins and the Kalends, Nones, Ides
The Roman calendar initially tracked lunar cycles and religious festivals, anchoring them to three fixed points: the Kalends (first day of the month), the Nones, and the Ides. March (Martius) was the first month, named after Mars, the god of war, reflecting a seasonal start to campaigning. May and June likely derive from goddesses Maia and Juno, while the names for July and August were later changes honoring emperors. The original ten-month year left winter as an unnamed gap, and later additions introduced January and February, bringing the calendar into partial alignment with the solar year through intercalary months and priestly intervention before the Julian reform.
January and February: Numbers and Purification
The shift from ten to twelve months
January (Ianuarius) and February (Februarius) were inserted around 713 BCE, possibly as late-comers after March. January drew its name from Janus, the two-faced god of thresholds and new beginnings, marking the start of the civil year. February came from februa, referring to purification rituals like Februa, a festival of atonement. Their positions at the year’s start in the Julian calendar helped synchronize civic and religious scheduling, while the numbering echoes an earlier ten-month count where they were originally the fifth and sixth months.
March, April, and May: War, Growth, and Spring
War, aperire, and Maia
- March (Martius): From Mars, Roman god of war; often the traditional start of the year in old calendars.
- April (Aprilis): Likely from aperire, Latin for 'to open,' linked to buds and spring, though connections to Aphrodite are speculative.
- May (Maius): Named for Maia, a Roman goddess associated with plant growth and fertility.
June and July: Juno and Julius Caesar
Goddess and dictator
June (Iunius) takes its name from Juno, goddess of marriage and the Roman state; the name may also play on the Latin iuvenis, 'youth.' July (Iulius) was renamed in 44 BCE to honor Julius Caesar after his Julian calendar reform, cementing a lasting political and cultural legacy. The Julian calendar introduced a more regular leap-year system, stabilizing the calendar and spreading month names across the empire’s administration.
August, September, October, November, December: Numbers Out of Order
September through December stem directly from Latin numbers: septem (seven), octo (eight), novem (nine), and decem (ten). When January and February were added at the beginning of the year, these months shifted to the fifth through tenth positions but kept their original numerical names, creating a permanent mismatch between names and order. August (Augustus) was renamed from Sextilis in 8 BCE to honor Emperor Augustus, cementing the trend of naming months after rulers and further tying the calendar to imperial authority.
Influences Across Languages and Calendars
Latin month names underpin many modern European names, often adapted through sound changes. Germanic languages, for example, reinterpreted Latin origins into distinct traditions. The Julian calendar’s widespread adoption preserved these names even as astronomical knowledge advanced. The Gregorian reform in 1582 refined the leap-year rule to realign the calendar with the equinoxes, but month names remained largely unchanged, ensuring continuity in civil, administrative, and cultural contexts across centuries.
Key Month Name Facts at a Glance
| Month | Origin / Meaning | Source Type |
|---|---|---|
| January | From Janus, god of thresholds and beginnings | Roman religion |
| February | From februa, a purification festival | Roman tradition |
| March | From Mars, god of war | Roman religion |
| April | Likely from aperire, 'to open,' or a connection to growth | Latin roots |
| May | From Maia, goddess of plant growth | Roman religion |
| June | From Juno, goddess of marriage and state | Roman religion |
| July | Renamed Iulius for Julius Caesar | Imperial renaming |
| August | Renamed Augustus from Sextilis | Imperial renaming |
| September | From septem, 'seven' | Latin numbering |
| October | From octo, 'eight' | Latin numbering |
| November | From novem, 'nine' | Latin numbering |
| December | From decem, 'ten' | Latin numbering |
Calendar Reform and the Enduring Use of These Names
The Julian and later Gregorian calendars standardized month lengths and leap-year rules while retaining traditional names, ensuring that month names remained anchored in both linguistic habit and state authority. Even as civil, religious, and astronomical calendars diverged in function, the shared month labels preserved an accessible link to ancient Roman timekeeping. This persistence reflects how deeply month names are woven into administration, culture, and everyday use, making them durable elements of language and time organization.