Years of Confusion: On the Peculiar Origins of Leap Years

by Michael Bedford

Published at 2024-02-27

We originally posted this in 2020, and now four years have gone by — quite quickly! And just like that, another leap year is upon us. Read on to find out why leap years exist at all!


“Thirty days have November, April, June, and September. With 28 there is but one. All the rest have 31,” but not this year. This year, none of the months have but 28. Instead, February has 29 days, so it seems this handy rhyme is in need of some amendment. How about, “All the rest have 31 but in a leap year you will find that February has 29.” We’re all used to this extra day intermittently throwing off this well-trod mnemonic, but why do leap years exist in the first place, and where did they come from?


Leaping into History

When in Rome

Julius Caesar, that controversial despot, has much to do with our modern-day calendar. Observant calendar users will note the sometimes-vainglorious tyrant’s name popping up in the summer — July for his own name, Julius, and August for Augustus, his heir. In addition to adding these two months to the calendar in an effort to align the calendar year with the tropical year, Julius Caesar also came up with the first system of determining which years should be leap years. Of course, all of this begs the question, “Why did Caesar make all these changes in the first place?” As with so many aspects of early civilization, it all comes back to farming.

Seeking to regularize planting and harvesting, Caesar’s modifications of the calendar allowed for easier annual planning. Noting that it took approximately 365.25 days for the Earth to orbit the sun, Caesar and his advisors came up with a plan to regularize the calendar year at 365 days per, adding an extra day into the calendar every four years. This system seemed to be working just fine, following a period of adjustment that culminated in what came to be known as the “last year of confusion,” but things still weren’t quite right. After a few centuries, the calendar again started drifting off course, and further reforms were made.


Come for the Calendar Reforms, Stay for the Chanting

By the 1580s, it was determined that the current calendar was off by approximately 10 days. Caesar’s system was better than the previous one, but it obviously still had some problems. So, it was up to Pope Gregory XIII to sort things out. First, to offset the 10-day discrepancy, Gregory decreed that October 15, 1582 should immediately follow October 4, 1582. Further, Gregory introduced what came to be known as the Gregorian calendar, which refined Caesar’s slightly trigger-happy model. Instead of continuing with Caesar’s system of having a leap year every fourth year, Gregory XIII instituted a few amendments.

To correct the overage of leap years, centennial years were all omitted from the leap year schedule. But, keeping things relatively confusing, Gregory XIII’s system further instructed that if a centennial year is divisible by 400 then it should be a leap year. This means that 1900 was not a leap year but 2000 was. The next centennial leap year, then, will be the year 2400.

The Gregorian system, with its minor adjustments, works quite well but is still only accurate to one day in 3,333 years. This means that we’ll have to decide by the year 5000 whether or not to add one more day in there somewhere.


Superstitions and Customs

Probably the most well-known leap-year custom is that of women setting aside gender normativity to propose to the men in their lives. This custom is apparently a result of St. Brigid convincing St. Patrick to allow women to propose to men every four years. There are a few different follow-ups to this custom, but my personal favourite is the one that states that if a man refuses a proposal from a woman during a leap year then he must purchase her 12 pairs of gloves so that she can hide for a year that she is not wearing an engagement ring. For savvy female glove-wearers, then, proposing during a leap year sets up a no-lose scenario: either he says yes and she gets a husband, or he says no and she gets free gloves for a year.

It’s considered inauspicious to get married during a leap year, and people born on February 29th, known as leaplings, are sometimes considered to have bad luck. On years without leap years, leaplings have the option of celebrating their birthdays on either the 28th of February or the 1st of March.


So, Do I Get an Extra Day or Not?

Since leap years last 366 days, one could make a good case for leap years truly having an extra day. This means that every four years, people procrastinating on filing their taxes or who can’t figure out what to get their friends who have birthdays on March 1st are granted an extra day to prepare. But, using that logic, that extra day gets whittled down to nothing with each passing non-leap year, so make sure you don’t procrastinate too much, or you run the risk of feeling the crunch when that extra day starts disappearing.



Michael Bedford is a freelance editor, copywriter, and performer living in Stoney Creek, Ontario. He can be reached at


Have an extra day to finish your writing? Then be sure to give us a call and we can get that edited for you! Take advantage of your extra day!