WHAT'S THE DEAL WITH LEAP YEAR?

When you were growing up, you may have learned how leap years work: we add a day every four years because it takes Earth about 365.25 days to go around the sun (one solar year).

But have you ever wondered what would happen if there weren’t leap days?

Would it really hurt if we always had 28 days in February?

Let’s just say that if we had no leap days, the world as we know it would be quite different.

The months in which various seasons happen would shift into other seasons; allowing winter to eventually happen in June, and summer to eventually happen in December.

The ancient Romans actually ran into some problems with their calendar because they didn’t have leap days to keep their calendar in line with the seasons.

Because of the shifting calendar, “the feast days of the Roman system were not in keeping with astronomical occurrences,” says Dr. Jeff Leigh, Associate Professor of history at the University of Wisconsin-Marathon County.

So Julius Caesar stepped in, adding several days to one particular year to set the calendar back to where it should have been, and then changing the calendar so that every four years, one day would be added to the year.

The problem with this “Julian Calendar” was that it actually takes closer to 365.2422 days (not an even 365.25) for the Earth to go around the sun, so after awhile, the calendar began to shift once again because it was off by 11 minutes and 14 seconds.

So, finally, in 1582, Pope Gregory XIII remedied the problem by removing some of the leap years.

In the Gregorian calendar (which is the calendar generally used in America), every century year (1700, 1800) is NOT a leap year, unless it’s divisible by 400.

So, for example, 1900 was not a leap year, but since you can divide 2000 evenly by 400, the year 2000 WAS a leap year.

But the calendar is still off by a little bit.

“It’s not perfect, it can’t be perfect, but it’s close,” says Leigh.

HOW DID WE GET CALENDARS IN THE FIRST PLACE?

All this talk about calendars might have you wondering how people ever came up with them.

“Calendars exist to tell us about the past, to organize the past, and to organize the future. Ritual dates are very important,” says Leigh.

People needed a way to remember when to celebrate certain rituals and holy days, but that wasn’t the only thing.

“If you want to set up a deal with somebody, you have to agree on when the trade will take place,” Leigh says, “Maybe even more importantly: agriculture. When do you plant? When do you harvest? It’s very important to know that this is an early frost or a late frost and not the coming of the next season.”

Eventually, people began using things like the sun and the moon as a basis for their various calendars.

The Gregorian calendar (used across America, and in many other countries), is based on the solar year, but some religions use calendars which are based on the orbit of the moon around the earth or both the solar and lunar orbits.