Why is February only 28 days long?

The Romans dedicated the month to the God of purification and left it with an even 28 days. February would then be moved after January in 452 B.C.

Why is February only 28 days long?
Scripps News

February is a busy month. You’ve got Super Bowl Sunday, Valentine’s Day, and Black History Month — just to name a few events. And unless it’s a leap year, we only have 28 days to fit it all in. So why is February the shortest month? 

To get answers we turn back the clock to 753 B.C. when the first Roman calendar included only 10 months. Each month had 30 to 31 days. 

Steve Case is a historian of astronomy and professor in the chemistry and the geosciences at Olivet Nazarene University.

"March was the first month, probably began pretty close to the spring equinox, the first day of spring," Case said.  

He broke down how the Romans calculated time. It included ancient astronomers measuring the cycles of the moon’s phases — known as the lunar calendar. 

"So your month would be maybe from when you can first see the crescent moon and reappear in the sky after new moon all the way through the cycle until it reappears in the sky again," he said. 

But changes were made in 452 B.C. by Numa Pompilious, the second king of Rome. Numa was superstitious and thought even numbers were unlucky, so he removed a day from the months that had 30 days. That left four months with 31 days and six with 29. 

The king wanted to sync the Roman calendar with the 12 lunar cycles, which take 354 days. So he had to add 56 days to the previous 298-day calendar. But to stick with the even number superstition, he added one extra day for a total of 355. 

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He split the remaining days to two months, with January at the beginning and February at the end of the calendar.  

"Mathematically, to have 12 lunar months, you have to have one month that has an even number. So that was February," Case said.   

The Romans dedicated the month to the God of purification and left it with an even 28 days. February would then be moved after January in 452 B.C. The problem was the lunar year was 10 days short compared to the solar year. And that caused its own set of challenges, since seasons are based on the Earth’s orbit around the sun.  

"After several hundred years you might have your, winter holiday — Christmas, for instance — being celebrated in a different season," he said.   

Enter Julius Caesar. In 46 B.C. he was a magistrate in the Roman Republic with authority to solve assigned issues. He replaced the Roman calendar with the solar calendar. And Caesar added 10 days to different months to bring the total to 365 days.   

Caesar added an extra day based on astronomer advice to account for the earth year being slightly longer than 365 days long, resulting in the shortest month known as February we know today.