MNA Feature Desk: The Roman dictator Julius Caesar is considered the “father” of leap year. The ancient Roman calendar system was based on a total of 355 days in a year—a full 10 ¼ days shorter than a solar year, which is the length of time it takes the Earth to make one complete orbit around the sun.
To keep the calendar system in line with the seasons, Roman officials were supposed to insert an extra month every so often, but by the time Caesar began to rule Rome, the calendar had gotten seriously out of whack.
Caesar consulted with the top astronomers of the day, and in 46 B.C. decided to add one day (known as an intercalary day, or leap day) every four years to make up the discrepancy between the lunar and solar calendars. Caesar also took the opportunity to rename Quintillis, the fifth month of the year (counting from March), leaving us with the month we call July today.
The leap year tradition took effect in 45 B.C., after a transition year that contained three extra months to make up for the difference that had accumulated over the centuries. The Julian calendar didn’t number days from “1” on up, but instead used calends (first day of the month), ides (middle of the month) and nons (in between).
The leap day was set on the day before the 6th of calends of March, so leap day originally came six days before the first day of March, or February 25 (as February normally had 29 days).
That might have solved the problem, except that a solar year is actually 11 minutes short of 365¼ days: It’s actually closer to 365.2425 days long (365 days, 5 hours, 48 minutes and 46 seconds).
Astronomers figured this out around the second century A.D., but the calendar system didn’t change, and by the 16th century it was nearly 10 days off-track, even with the leap year system. In 1582, Pope Gregory XIII made his own reforms to the Julian Calendar, restoring the vernal equinox to March 21 from March 11, and producing the calendar system most of us use today.
Leap Year Trivia
- Did you know that according to the Gregorian calendar, leap year doesn’t occur exactly every four years? That’s right—Gregory was even more precise that that, and made leap year occur in years divisible by four, except for those divisible by 100 and not divisible by 400. Confusing enough for you? In effect, that means that 97 out of every 400 years are leap years, including the century years 1600 and 2000 but NOT 1700, 1800 and 1900.
- According to British tradition, a leap day is the only day of the year a woman can propose marriage to a man. As legend has it, in fifth century Ireland, St. Bridget complained to St. Patrick about the fact that women had to wait for men to propose. So Patrick allowed women one day every four years to take the initiative. The tradition became the basis for Sadie Hawkins Day in the United States, first dreamed up by Al Capp in his cartoon serial “L’il Abner” and celebrated either on February 29 or November 15, the day the first L’il Abner comic appeared.
- Because Greek superstition holds that marrying in a leap year brings bad luck, as many as one of every five Greek couples avoid planning their weddings in a leap year.
- The first warrants for arrests in the Salem witchcraft trials were issued on February 29, 1692.