For centuries, attempts to sync calendars with the length of the natural year have sowed chaos—until the concept of leap year provided a way to make up for lost time. The solar year is approximately No calendar comprised of whole days can match that number, and simply ignoring the seemingly small fraction creates a much bigger problem than one might suspect. Humans have long organized our lives in accordance with what we've observed in the skies.
Ancient Egyptians planted their crops each year on the night when the brightest night star disappeared, while historians in ancient Greece and Rome also relied on the positions of the stars to anchor events in time. Religious leaders expected feast days to align with certain seasons and lunar phases. That's why most of the modern world has adopted the Gregorian calendar and its leap year system to allow days and months to stay in step with the seasons. Early Egyptians prior to about B.
But lunar months average So societies that kept lunar time quickly drifted well out of sync with the seasons due to the day lag. Other ancient calendars, dating to the Sumerians 5, years ago, simply divided the year into 12 months of 30 days each. Their day year was nearly a week shorter than our annual journey around the sun.
By the time Julius Caesar enjoyed his famed affair with Cleopatra, Rome's lunar calendar had diverged from the seasons by some three months—despite efforts to tweak it by irregularly adding days or months to the year. Caesar adopted the system by decreeing a single, day-long Year of Confusion 46 B. He then mandated a But even this system was flawed, because the quarter of a day that leap year adds annually is a bit longer than the solar year's leftover 0.
To address the discrepancy between the old Roman calendar and the new one, Caesar made that first new year days long. It would take decades for the new calendar to be widely observed, but the problem should have been solved. Except for one thing: an actual solar year is not days and 6 hours long. The average established by Caesar was only a little bit off—it was 11 minutes and 14 seconds too long—and Europeans kept using it for the next thousand-plus years.
By though, those 11 minutes per year had accumulated to a 10 day discrepancy. As a result, in the year , Oct. In keeping with the Roman tradition of messing with the length of February, that day would fall in the second month of the year—thus Leap Day was born.
By the 16th century, scholars had noticed that time was still slipping—Caesar's calculation that a year lasted This was a problem for the Catholic Church, as the date of Easter had drifted away from its traditional place, the first Sunday after the first full moon following the vernal equinox, by roughly ten days.
Pope Gregory XIII commissioned a modified calendar, one which kept Leap Day but accounted for the inaccuracy by eliminating it on centurial years not divisible by , , and were not leap years, but was. The introduction of the Gregorian Calendar marked the last change to the Western calendar as we know it today.
Experts note that the Gregorian calculation of a solar year— Thankfully, the Gregorian calendar is only off by about one day every 3, years, so mankind has some time before this becomes a problem. Curiously, many Leap Day customs have revolved around romance and marriage. Tradition holds that in 5th-century Ireland, St. Bridget lamented to St. Patrick that women were not allowed to propose marriage to men.
While he was making the fix, Julius also decided to give his name to the month of July. Although Caesar decreed the new calendar in 46 B. The first add-a-day leap year was 45 B. The new Julian leap day wasn't added at the end of February originally, but on the day preceding the 6th of the calends of March.
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