Are There Potential Alternatives to the Leap Year System?

I know leap years keep calendars in sync with the solar year. But why haven’t we found a less clunky system?

—Dave T., Chicago, Ill.

It’s not that we don’t keep trying. One proposal calls for a 364-day year, with exactly 52 weeks, that keeps each date on the same day of the week every year. How convenient, right? Holidays would always fall on the same day of the week, school would start on the same date every year, and if you were born on a Sunday, you would celebrate your birthday on a Sunday. But there’s a teensy drawback: Every five or six years, you would have to add a week at the end of December!

The problem lies in the way our solar system works (meaning: the time it takes for Earth to rotate on its axis and the time it takes for Earth to revolve around the sun). Consistent calendars experience a drift in the seasons because the time in a solar year (about 365 days, 6 hours) cannot be evenly divided by the time in an earthly day (about 23 hours, 56 minutes).

Most years that can be evenly divided by 4 are leap years. But even adding a day every four years doesn’t fix things. A century year, such as 1800, 1900 or 2000, can be evenly divided by 4, but it’s not a leap year unless it can also be evenly divided by 400. So 2000 was a leap year, but 2100 will be a regular year. And this is only a patch! (It will work for about 3,300 years, at which point we’ll be a day off again.)

The century rule was added in 1582 when Pope Gregory XIII, whose calendar we use today, patched the one introduced by Julius Caesar in 46 B.C., which had become more than a week off. So he also decreed Oct. 4 would immediately be followed by Oct. 15. And yes, he took some flak for this! People were convinced he had taken 10 days from their lives, and many countries declined to go along. Until 1752, on the day calendars read Jan. 17 in England, for example, they read Jan. 28 in Catholic Europe. Russia didn’t give in until 1918, and Greece held out until 1923.

But the continued effort is worth it: No one wants winter to someday arrive in July!