I remember my confusion as a child when I discovered one of my classmates only had a birthday every four years. Later on, I figured out the real reason was my classmate was born on Feb. 29.
Being a leap year baby has more drawbacks than celebrating true birthdays every four years. Many people move their birthday to Feb. 28 or March 1.
The problem extends further into unthought of accounts. Think about somebody who usually celebrates their birthday on Feb. 28 trying to go into a bar for their 21st birthday. The bouncer could let them in even though they aren’t technically legal yet, or they could be refused and told to come back tomorrow.
There are not many age dependent laws that take a leap year baby into account, and that can cause some major buzzkills when people turn 18 or 21, but the existence of leap year is an important thing for science and the accuracy of our calendars.
When we were taught the calendar year has 365 days every year, Feb. 29 is the exception. This extra day creates a calendar year with 366 days instead and is used to keep our calendars accurately in sync with the seasons and orbit of the earth.
These added days are calculated by two different types of calendars. The two calendars are known as the Julian calendar and the Gregorian calendar. Jeffrey Shallot, from the University of Waterloo, wrote an article that explains the differences between these two calendars.
According to “Pierce Expansions and Roles for the Determination of Leap Years” by Jeffery Shallit, an extra day was added every fourth year in the Julian calendar. This meant every year a quarter of a day was added to the 365 days until it reached 366, then the cycle restarted.
The Gregorian calendar is similar, but it excludes century years unless it is divisible by four. For example, 1900 was not a leap year under the Gregorian calendar but 2000 was a year that had a leap day in it, because 2000 can be divided by four to equal 500.
Today the Gregorian calendar is used because it is mathematically more accurate than the Julian calendar. This means that the average length of a year, according to the Gregorian calendar, is closer to the current average year length than the Julian calendar.
According to “New Year’s Day and Leap Year in English History” by A. F. Pollard, Julius Caesar was the one that implemented the Julian calendar. His astronomical advisors discovered that there were about six hours more than an exact 365 days. I couldn’t imagine figuring out with a calculator, much less without one.
It makes sense the extra day is added onto the shortest month of the year. The new year of the old Roman calendar began in March, which is why the intercalated day was tacked on at the end of February. That is also why February is so short compared to the other months.
Caesar later changed the start of the new year from March 1 to Jan. 1, but the placement of the extra day remained the same.
The biggest misconception I had when I was younger about leap year, was that people born on a leap day didn’t celebrate like others.
Leap day babies are normal people just like the rest of us. They age a year at the end of every February and unfortunately, they don’t have any cool anti-aging superpowers that come with being born on a day that only shows up every once in a while.
Anteia McCollum can be reached at [email protected]
Christian
Caesar didn’t change the start of the new year. It was the second Roman king, Numa Pompilius, who was credited with that change, and Numa lived six centuries before Caesar’s time. (Numa was also credited with introducing the months of January and February; previously, the days of the year after December and before March were not associated with any month.) Prior to Caesar’s calendrical reform, the Roman calendar had a common year of 355 days, and a leap year would receive a separate leap month, either 22 or 23 days in length, which was inserted before the last five days of February. In the old Roman calendar, a common year would have a 28-day February, but a leap year would have the first 23 days of February, then the leap month, then the last five days of February! Caesar’s replacement of the leap month with the leap day inserted the leap day where the leap month used to be, so that it wouldn’t interfere with the existing sacred days of the calendar. As a result, in a 29-day February, it was February 24 that was the original leap day, and February 24 through 28 in a common year became February 25 through 29 in a leap year due to how Romans reckoned dates. In Latin, the last day of February was called “pridie kalendas martias” (“the day before the Kalends of March”; the Kalends were always on the first day of a month). The day before that was called “ante diem III kalendas martias” (“the third day before the Kalends of March”; counting in Latin is inclusive of the starting point, so “III” includes the Kalends itself). Similarly, “a.d. IV kal. mart.” is three days before the Kalends, “a.d. V kal. mart.” is four days before, and “a.d. VI kal. mart.” is five days before. In common years, “a.d. VI kal. mart.” is February 24, and “a.d. VII kal. mart.” is February 23. After Caesar’s reform, in a leap year, “a.d. VI kal. mart.” is February 25, but “a.d. VII kal. mart.” is still February 23, since that was the sacred Terminalia festival. As a result, the leap day February 24 was called “a.d. bis VI kal. mart.”, or “ante diem bis sextum kalendas martias”—“the second sixth day before the Kalends of March”. The Latin phrase “bis sextum” is the source of the English word “bissextile”.