Why Does February Only Have 28 Days?

February is a bit of an odd-month out, containing at least two full days less than other months — not to mention the random 29th day popping out every four years on leap year.

So what’s the deal with February? Why is it the only month to end with 28 or 29 days, and why does leap year even occur, anyway?

Let’s find out!

Why is Leap Year on February 29?

The Romulan Calendar

To understand the thought and reasoning behind giving just one month of the year 28 days (and sometimes giving it 29), we have to go back to the place that gave us the calendar we use today — Ancient Rome. 

In fact, we have to go back to the very first years of Rome’s existence, under the reign of Romulus, the first king of Rome, in 753 B.C..  

Back then, those parts of the world knew of two different calendars. First was the solar calendar, which measured 365.242 days in a year using the equinoxes and solstices observed during the sun and stars’  passage around the Earth (as they were believed to have done back then).  There was also the lunar calendar which tracked the 12 lunar cycles per lunar year, with each cycle containing around 29.5 days, adding up to 354 days a year. 

Though the solar year and lunar year contained different days, one could still correctly measure the passage of time with them, but only the solar year could accurately measure a full trip around the sun and correctly predict the seasons. It could be tricky to track the days in the 360+ day year, and in a burgeoning society like early Rome, a more efficient method was needed to keep track of dates, events, holidays, religious festivals and the like. 

To solve his scheduling issues, Romulus developed a calendar that contained 10 months with either 30 or 31 days in them, assembled as follows:

• Mensis Martius, “Month of Mars” with 31 days
• Mensis Aprilis, “Month of Apru (Aphrodite)” with 30 days
• Mensis Maius, “Month of Maia” with 31 days
• Mensis Iunius, “Month of Juno” with 30 days
• Mensis Quitilis, “Fifth Month” with 31 days
• Mensis Sextilis, “Sixth Month” with 30 days
• Mensis September, “Seventh Month” with 30 days
• Mensis October, “Eighth Month” with 31 days
• Mensis November, “Ninth Month” with 30 days
• Mensis December, “Tenth Month” with 30 days

Now, if you’ve got any experience with basic addition, you’ll notice that this calendar contains a total of 304 days, matching neither the lunar year nor the solar year quota. An absence of 61.25 days, no less! 

Their solution? Scholars are not entirely sure. Some historians say that days were added to months haphazardly until the calendar reset itself. Others say that the days after December were just seen as “winter” and were therefore not tracked. 

Same, honestly. #hibernate

Either way, the Romulan calendar wasn’t around for long before someone decided to reform it — which leads us to the Republican calendar. 

The Republican calendar

Rome’s second king, Numa Pompilius, came into power in 715 B.C. after the death of Romulus in 716 B.C.. And just as his predecessor gained legendary status in history, so did Numa. 

Numa Pompilius was a strong character who influenced much of Roman life, religion and politics. His devotion to the Roman gods and goddesses placed him in high regard with the Roman people who, up to the creation of the Republic of Rome, were more warlike than civilly organized. His apparent wisdom, sovereignty and piety placed him in the pages of history books and gave him great influence among Roman society. Numa is also credited with the creation of several religious and political cults, including the Vestal Virgins, the Cults of Mars, Jupiter, Termius and Romulus, and the pontifex maximus. 

All that to say that Numa Pompilius was a great figure in early Roman history, and he was the one to revise the confusing Romulus calendar into a more digestible and mathematically-accurate one.

Ultimately, several factors played into the creation of Pompilius’ new calendar: superstition, politics and religion.

First, Pompilius removed one day from every even-numbered month in the Romulan calendar, bringing the yearly total to just 298 days. Why? Because even numbers were bad luck in Ancient Rome, so out went a whole day from Aprilis, Iunius, Sextilis, November and December.

The next thing Numa Pompilius did was to incorporate the lunar cycle into the new calendar; or at least, aspects of the lunar cycle. He wanted 12 months in his calendar year to cover the lunar year, which itself was 354 days. And, of course, even numbers were bad luck, so he moved his goal to 355 days instead. 

With his current 298-day year coming a full 57 days short of his lucky-numbered lunar year, Pompilius took the remaining days and split them up into two months. He added the newly formed Mensis Ianuarius (“Month of Janus”) and Mensis Februarius (“Month of Februa”) to the calendar after Mensis December, with 29 and 28 days each, respectively.

And, yes, the whole even-numbered thing was a big no-no in Rome, but Februum is Latin for “purification” and the entire month was dedicated to ritual and to the preparation of the dead. So if there was a mathematical requirement to have just one even-numbered month to make an odd-numbered year, then Mensis Februarius might as well be the month to take it on. 

But wait! There’s still more!

This new calendar had a few issues, but the most glaring one was that the calendar was 10 days short of a full solar year, even though it hit the mark on lunar cycles. Too many years of being 10 days short would put the seasons totally out of whack and would get in the way of agriculture, harvesting and trade. 

To account for the missing 10 days, Pompilius’ calendar included Mensis Intercalaris every other year after February. This “Intercalary Month” would alternate with 27 days one occurrence and 28 days the next, so that after four years (one cycle), the days would add up to the amount of days in four solar years. Then, the whole process would start again. 

This method would have worked in theory, because every four years the Republican calendar would have matched up with the solar calendar and the cycle would have reset itself. However, the system didn’t work in practice: politicians would stretch out the Intercalary month to extend their terms; if Rome was at war, the month might go forfeit; if someone forgot to track it, then it wouldn’t be tracked.

In short, it needed an upgrade.

The Julian calendar

Centuries later in 46 B.C., Julius Caesar came to power and ordered a reformation of the outdated Republican Calendar. 

Caesar had spent extensive time in Egypt and had seen the solar calendar being used with great effectiveness, as displayed by the use of the Zodiac calendar to measure the passage of time using the sun and stars. Using the existing Republican calendar as a basis, Caesar added the missing 10 days back into the existing months and got rid of Mensis Intercalaris altogether, bringing the total number of days in the calendar year to 365. He also officially shifted Mensis Ianuarius and Mensis Februarius to the beginning of the calendar, creating the structure that we still use today.

Caesar also knew that a true solar year was just a hair over 365 days — 365.242 to be exact. So, he added a leap day in between the 23rd and the 24th of Mensis Februarius that would occur every four years. Thus, creating the day, month and year structure that we still use today!

Today’s calendar

Since Julis Caesar and his nephew Augustus Caesar’s reign, few things have changed to their Julian calendar. The leap day was moved to February 29 rather than after the 23rd, and Pope Gregory XIII made a few changes to the exact length of the year which, in the end, created the much more accurate Gregorian Calendar that we still use today. 

Both Julius Caesar and Caesar Augustus are honored for their work in establishing the modern calendar through their names. The month of Quitilis was renamed to July in honor of Julius, and the month of Sixtilis was renamed to August for Augustus, who helped get the calendar implemented smoothly following Julius Caesar’s assassination.

It turns out that there are a lot of reasons why February has just 28 days, and sometimes 29. It’s a little bit because of superstition, a little bit about mathematics and a little bit about the moon, sun and stars— but in the end, February’s strangely-numbered days are essential to measuring the passage of our little planet through time.

They quite literally help make the world go round. 

Happy February!

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Featured photo courtesy Pixabay/tigerlily713