How many months of the year have 31 days?
And the answer: seven.
There are seven months of the year that have 31 days: January, March, May, July, August, October, and December. Four other months have 30 days, while February has either 28 or 29 days, depending on the year.
Romulus, the founder and first king of Rome, had a problem. With an increasing number of festivals, feasts, and religious celebrations across the empire, Romans needed a way to keep track of everything. In other words, ancient Romans needed a calendar. While ancient astronomers had accurate calculations for the time between equinoxes – or solstices – nature had already given them an easier way to watch the days go by: the lunar calendar. This meant that early Roman people followed the phases of the moon (approximately a 29.5 day cycle) to count their months.
Yet, there was another problem with that system: the Romulan calendar only had 10 months of either 30 or 31 days, beginning in March and ending in December. As a result, the calendar was about 61 days too short. Though, because Romans tended to be preoccupied with surviving the winter during those 61 days, and began their year on the new moon of the spring equinox, they weren't too concerned with the lack of timekeeping during the stretch of cold months.
The following ruler of Rome, Numa Pompilius, had a new idea. Even numbers were bad luck in ancient Rome, so the ruler removed a day from all the even numbered months and tacked on two more months at the end of the year: Januarius and Februarius (sound familiar?) to complete twelve lunar cycles in a given year. But, like his predecessor, Numa's calendar didn't add up to anywhere close to the actual number of days it takes to complete one full rotation around the sun. So then what?
By the time Julius Caesar came to power, things had gotten pretty confusing. Caesar had spent a lot of time in Egypt, where 365 day calendars were the primary form of timekeeping, so, in 46 BCE, Caesar ditched the lunar calendar for a more effective system: the solar calendar. January and February had already been moved to the beginning of the year, and Caesar added ten days to various months to get a total of 365. And, because a tropical year is slightly over 365 days, he tacked on an extra to February every four years.
And now, a joke.
What did the calendar say after Tuesday?
WTF!
