The Gregorian calendar is used today, but it is based on the ancient Roman calendar, which is thought to have been invented by Romulus, the first king of Rome, around 753 BC.
The Roman calendar, which was based on a complicated lunar calendar, had 12 months, but only 10 of them had formal names. Winter was essentially a “dead” period during which the government and military were not active, so they only had names for March through December. Because this was the month when active military campaigns resumed, March (Martius) was named after Mars, the god of war. May (Maius) and June (Junius) were named after goddesses Maia and Juno, respectively. The month of April (Aprilis) is thought to derive from the Latin aperio, which means, “to open,” a reference to the springtime buds opening. The remaining months were simply numbered, with their Latin names referring to the fifth (Quintilis), sixth (Sextilis), seventh (September), eighth (October), ninth (November), and tenth (December) months, respectively.
January (Januarius) and February (Februarius) were eventually added to the year’s end, giving each of the 12 months a proper name.
The month of January was named after Janus, the Roman god of beginnings and transitions, while February was named after Februa, an ancient springtime festival dedicated to ritual cleaning and washing.
Updates to the Julian Calendar
When Julius Caesar was elected Pontifex Maximus, he changed the Roman calendar to one based on the Earth’s rotation around the Sun. It was a solar calendar, similar to the one we use today. To keep the calendar year aligned with the solar year, January and February were moved to the front of the year, and leap years were introduced.
The months of January and February were marked by reflection, peace, new beginnings, and purification. Quintilis was renamed July in honour of Julius Caesar in 44 BC, and Sextilis was renamed August in honour of Roman Emperor Augustus in 8 BC, after Caesar’s death.
Naturally, all of the renaming and reorganising meant that the names of some of the months no longer corresponded to their positions in the calendar (September to December, for example). Later emperors attempted to rename the different months after themselves, but their efforts were short-lived!
Gregorian Calendar
Because there were still some inaccuracies and adjustments to be made, Pope Gregory XIII introduced several reforms to the Julian calendar in 1582. The Gregorian calendar shortened the calendar year from 365.25 days to 365.2425 days because the Julian calendar overestimated the time it took the Earth to orbit the Sun. This allowed leap years to more easily correct the calendar, bringing the equinoxes and solstices—and thus the date of Easter—back into alignment with their observed dates.
January
Janus, the Roman god of beginnings and endings, is the month’s name. Janus was the god of doors and gates, which seems fitting for the New Year. He is frequently depicted as having two faces, one looking forward and the other backward. January was the tenth and final month to be added to the calendar, which began in March with ten months.
February
The month of February is named after a Roman purification festival called februa, which took place on February 15. Februa translates to “cleansing month,” a fitting moniker given that February was once the year’s final month. A “month of cleansing,” similar to today’s New Year Resolutions, appears to be a good way to say goodbye to the old and welcome in the new.
March
Mars, the Roman god of war, is commemorated in March. During the time of celebration between the old and New Year in ancient Rome, war was prohibited. March was originally the first month because it was the first month of the year when the weather was mild enough to resume warfare.
April
There are a few different theories about the origins of the name April. April is thought to be derived from the Latin base apero, which means, “second,” because it used to be the second month of the year. Others claim it comes from aperire, a Latin word that means, “to open” and is associated with the opening of buds and flowers in the spring. Others claim that Aphrodite, the Greek goddess of love, beauty, and procreation, was the inspiration for April’s name.
May
Maia, the Greek goddess, is honoured in May. She was an earth goddess and a goddess of growth, which explains her connection to this springtime month. She had a son, Hermes, with the god Zeus, and she was an earth goddess and a goddess of growth.
June
June is named after Juno, Jupiter’s wife and goddess’s queen. Juno was the patroness of childbirth and marriage, which is fitting for the month of weddings, which has long been the most popular.
July
Julius Caesar was born in July, and the month was renamed after his death in 44 B.C. July was previously known as “Quintilis,” which is Latin for “fifth,” and referred to the fact that July was the fifth month of the calendar year, which began in March. July was also the first month not named after a Roman or Greek deity, but after a real person.
August
August is the only other month with a historical figure named after it: Augustus Caesar, Julius Caesar’s nephew and Rome’s first emperor. August, like July, was previously referred to as “Sextilius,” which meant “sixth.” Emperor Augustus’ legacy was the source of the adjective august, which means “respected and impressive.” Furthermore, both July and August were given thirty-one days to reflect the importance of the leaders they represented.
September, October, November, and December
September, October, November, and December are derived from the Latin words septem, octo, novem, and decem, which translate to “seventh,” “eighth,” “ninth,” and “tenth,” respectively. Though their root meanings now make them feel out of place in the calendar year, they were, in fact, the seventh, eighth, ninth, and tenth months before the addition of January and February.
The names of the months come from three different places: Greek and Roman gods, Roman rulers, and numbers.
Also published on Medium.