It’s an odd contradiction: December, whose name comes from the Latin decem (“ten”), is the 12th month of the year. The mismatch isn’t a mistake — it’s a relic of a calendar long since restructured.
In ancient Rome, the calendar once began in March, making December the 10th and final month of the year. This early system, attributed to Romulus (founder of Rome alongside twin Remus), included only 10 months, leaving the winter period unaccounted for — a kind of calendrical limbo.
That changed around the eighth century B.C. when King Numa Pompilius added January and February to the calendar to cover the monthless winter. Still, March remained the official start of the year for centuries.
In 153 B.C., the College of Pontiffs shifted the beginning of the year to Jan. 1 to better suit civic needs. The move pushed December from 10th to 12th place — yet its name never changed.
But it didn’t stop there. September (septem, “seven”), October (octo, “eight”) and November (novem, “nine”) all retained their numerical names, even though their positions shifted two places later in the year.
So, when you count down to New Year’s Eve, remember: December didn’t always hold the 12th spot. It once stood as the 10th chapter in a shorter story — until time itself was rewritten.