This year, February has one extra day — a gift from the ancients who were never able to solve the fundamental problem of syncing the calendar year with the solar year.
Early efforts to create the correct time for more than a couple of years involved various methods including trying to use a lunar year or attempts at creating a solar calendar.
“It all comes down to the fact that the number of Earth’s revolutions about its own axis, or days, is not connected in any way to how long it takes for the Earth to get around the sun,” says John Lowe, who led the National Institute of Standards and Technology (NIST)’s Time & Frequency Division.
As it turns out, we humans are very clever creatures and don't need ancient astronauts telling us how to build the pyramids or the Easter Island statues or even whispering in Einstein's ear the theory of relativity.
And we sure as hell don't need aliens solving the mystery of how to sync our calendars so they show the proper number of days.
But like many human inventions, it took a lot of failed tries and some great good luck to finally come up with almost the right answer.
At one time, lunar calendars were all the rage in the ancient world. But there was a huuuuge problem: the lunar month is only about 29 days long and only 354 days for the year. The Egyptians and Romans solved it by just adding a five-day festival at the end of their year.
Nice party, but there was still about a quarter of a day discrepancy that would rear its head over a few years. Once Egyptians sobered up, they knew they had to change things.
When Julius Ceasar conquered Egypt and was having his red-hot affair with Egypt's rather homely queen Cleopatra, he noticed Egypt's 365-day year with a leap day added every four years. Ceasar wanted to adopt a similar calendar for Rome, but he had to sync up the two calendars. Being Ceasar, he declared a 447-day year for one year to accomplish the syncing.
It took a pope tapping some of the greatest mathematical minds of the Catholic church to solve the problem and bring order out of chaos.
Between the time Caesar introduced the system and the 16th century, this small discrepancy had caused important dates, including the Christian holidays, to drift by some 10 days.
Pope Gregory XIII found the situation untenable, so his Gregorian calendar was unveiled in 1582—after another drastic adoption of time-warp tactics.
“Gregory reformed the calendar and they dropped ten days from the month of October that year,” Evans says. “Then they changed the leap day rules to correct the problem.”
Now leap years divisible by 100, like the year 1900, are skipped unless they're also divisible by 400, like the year 2000, in which case they're observed. Nobody alive remembers the last lost leap day, but dropping those three leap days every 400 years keeps the calendar on time.
"There's nothing sacrosanct about locking a calendar to the solar year the way ours is," says James Evans, a physicist at the University of Puget Sound and editor of the Journal for the History of Astronomy. "People can get used to any calendar system. But once they are used to it what really seems to rile them up is when something is changed."
As I mentioned at the top, the current Gregorian calendar we use isn't perfect. The exact length of the year is 365.2425 days. This is 30 seconds longer than the solar year and, as Nat Geo points out, "At such a rate it will take 3,300 years before the Gregorian calendar moves even a day from our seasonal cycle."
So we've got some time before we have to prepare for the change.
The big reason for all these changes to calendars over the last 5,000 years has been the need for accurate timekeeping for planting crops. The ancients couldn't depend on a lunar cycle to grow food. Toward the end of the Roman empire and the Cesarean calendar, there was virtual chaos in Christian Europe as the time to plant got further and further from the optimal time to plant.
Pope Gregory brought order to chaos and made possible the great advances in science and technology we enjoy in the modern world.
