Some months have 30 days and others have 31. And then there’s weird old February, packing a scant 28 days (or 29 in a leap year). Why are you so short, February?
The Romulus calendar
In the eighth century B.C., the Roman Empire operated via the Romulus Calendar, a 10-month system that started in March (or Martius) and concluded in December. Each month (Aprilius, Maius, Junius, etc.) had 30 or 31 days, mostly alternating, and it all added up to 304 days. You’ll notice that there’s a substantial gap between the Romulus Calendar’s number of months and days and the calendar we use today, such as the complete lack of January and February. Well, at the end of that ancient Roman calendar, there was a nameless 61-day period of winter that the Romans didn’t even count or label.
The new 12-month calendar
In 713 B.C., two years after Numa Pompilus became the second king of Rome, the new leader commissioned a new calendar, because he thought it was strange to use such an imperfect date-numbering system. His advisors came up with a new, 12-month calendar based on the year’s 12 lunar cycles, which added up to 355 days. One problem: Romans were superstitious about even numbers, and Pompilus didn’t want a year or month to end in an even number, so they all consisted of 29 or 31 days. To get to 355 days, one month would have to be even, and that honor fell to one of the two new months. Januarius and Februarius came at the end, after December, and Februarius wound up with 28 days instead of 29.
Remember Mercedonius, the extra month?
But that calendar was a little short, and the seasons and cycles soon fell out of whack with what the official Roman calendar said they ought to be. So, the Roman government came up with Mercedonius, a 27-day extra month. Leaders decided to end Februarius early, on the 24th, to accommodate the extra month. That overcorrection led to mass confusion throughout the Roman Empire for decades about what day it actually was. A few years into his reign, Julius Caesar instituted calendar reforms. To get things even, the year 46 B.C. lasted for a whopping 445 days, after which a new, sun-based calendar entered use, finding that a year was actually closer to 365 days. And if it ain’t broke, don’t fix it — February remained 28 days through it all.