The Odd Month Out: Why February only has 28 Days

It’s extremely easy to forget that while all of the other months of the year have 30 or 31 days, February ends on the 28th, or on a leap year, the 29th. Find it weird that it’s March already?

Well, the reason that February is cut short dates back to the second king of Rome, Numa Pompilius. Rome’s lunar calendar was at first 10 months long, starting in March and ending in December. The first king of Rome, Romulus, led his people to find the time of March to December unimportant because it didn’t affect the Harvest.

*Egeria Gives the Laws of Rome to Numa Pompilius*, Anna Ottani Cavina, Spanish Embassy to the Holy See, Rome, 1806.

But when Numa Pompilius became ruler, he wanted to make the calendar more accurate by lining it up with the 12 lunar cycles in a year. The previous calendar had had 6 months of 30 days and 4 months of 31, for a total of 304 days. But since Numa didn’t want to have even numbers in his calendar due to superstition, he subtracted a day from each of the 30-day months to make them 29. This made the year 355 days, so he added January and February to make up for the time they lost.

Romans thought that even numbers were unlucky, so they made each month an odd number of days (either 29 or 31). To get to 355 days though, one month had to be an even number. So why did they choose February to be the one that ends on the 28th? It is possible that this is because February was when the Romans honored the dead and performed rites of purification; the word “februare” even means “to purify” in the dialect of the ancient Sabine tribe.

After a few years of using Numa Pompilius’ new 355-day calendar, they realized that the months and seasons were falling out of sync. To try and realign them, the Romans added a 27-day leap month when needed. The problem was that the leap month was too inconsistent, so in 45 B.C, Julius Caesar had an expert create a sun-based calendar similar to that of the Egyptians. This new calendar added about 10 days to each year to make each month either 30 or 31 days long, excluding February. Because the calendar is exactly 365.25 years long, one day was added to February every four years, which we now call a “leap year.” So most of the time, February was left with just 28 days!