After that, he looked to Egypt's calendar for inspiration and made the years 365.25 days long, adding an extra day every four years, without accounting for the century year loophole.īy the time we reached the 16th century, the calendar needed to be reworked again, due to Christian holidays and some inconsistencies. After Rome's lunar calendar diverged from the seasons by months, Caesar instituted a 445 day so-called 'Year of Confusion' in 46 B.C. Rome's Julius Caesar eventually established a leap day outside of Egypt. They just added an extra five days of festivals, of partying, at the end of the year.' Sounds like we should take a cue from ancient Egypt! John Lowe, who led the National Institute of Standards and Technology (NIST)'s Time and Frequency Division, stated, 'When the Egyptians adopted this calendar they were aware that there was a problem. However, there were still problems with this system. Before 3100 B.C., the early Egyptians, Romans, and Sumerians used lunar calendars to track time, but they also had to add extra days to make their calendars match the Earth's orbit. Getty Images Who came up with the idea?Īccording to National Geographic, the idea to add extra days to our calendar dates back centuries. First, that it's evenly divisible by four and, second, years that are divisible by 100 (century years such as 1900 or 2000) can't be leap years unless they are also divisible by 400 (1900 was not a leap year, but 2000 was). In essence, for a year to be a leap year, it must follow two rules. The Old Farmer's Almanac explained the math behind leap years. You can expect a leap year every year that's divisible by four, though with a few exceptions. February 29th is always the day added to the calendar on a leap year, and it's known as leap day. What is a leap year?īasically, it's year with 366 days instead of the usual 365. Here, we explain some leap day facts, debunk some myths, and answer all of your questions about this odd quirk in our calendars. Whether you're upset that the day prolongs the wintery month of February or looking forward to the extra time, leap day certainly brings about opinions and much confusion.

The elusive February 29th shows its face once again at the end of this month, giving us all some bonus time in 2020. While this still doesn’t perfectly line up with the solar year, it will be 3,300 years before this calendar begins to diverge from our solar year by a day.You might have noticed that the calendar has an extra day this year. This makes the average year 365.2425 days long – much closer to the solar 365.2422-day year. Since 365.25 days, while close, is still longer than the 365.2422-day solar year, Pope Gregory XIII eventually created the Gregorian calendar that we currently follow in which a leap day is occassionally skipped. After this, he ordered a 365.25-day year with a leap day added every four years.īut even this change wasn’t good enough. The idea behind this decree was to all at once correct the damage that had already been done from years of drifting out of sync with the seasons. In 46 BC, Julius Caesar declared they would, for just one year, take on a 445-day calendar he called the Year of Confusion. But the Romans were still behind, trying to adjust their calendar by randomly adding days or months here and there. The Egyptians eventually began observing a 365-day year with a leap-year system. The Egyptians who adopted this calendar attempted to solve that problem by adding an extra 5 days of festivals and partying at the end of the year. With just 360 days, this calendar was an entire week shorter than the Earth’s orbit around the sun. The ancient Sumerian calendar of 5,000 years ago very simply divided the year into 12 months with 30 days each. ‍Throughout history, humans have dealt with the fact that the solar year doesn’t line up with our calendar in many different ways. see our handy chart above to help you easily determine when it’s a leap year! History of Leap Years 1600, 2000, etc.), then it actually is a leap year. However, if it is divisible by 100, but also divisible by 400 (i.e. To put it as simply as possible, if the year is also divisible by 100 (i.e. 2012, 2016, 2020, 2024, etc.), but there are some exceptions to this rule, which can get kind of confusing.

We all know that leap years are the years that are divisible by 4 (i.e.

Was 2000 a leap year