Leap Days and Leap Years:

How and Why History Gave Us Such a Confusing Calendar

by Max Lien, age 15

    Julius Caesar founded the leap day in 46 B.C., effective in 45 B.C. His leap day added ten days to the Roman calendar. Centuries later, when Pope Gregory XIII was elected in 1572, he felt that all the Christian holidays were being celebrated on the wrong dates due to Caesar’s leap day. To fix this, the Pope asked astronomers to produce a different calendar, known as the Gregorian calendar. The Gregorian calendar has 12 months and about 365 days, with a leap day once in a while. This is the calendar that the majority of the world uses today.
    The Gregorian calendar does not have exactly 365 days. It is actually
365.242199 days. This means that if we only count 365 days in a year, we miss the extra 0.242199 of a day. We make up for this by adding a leap day to every year evenly divisible by four, or every four years.
    However, it is not so simple. Since the "leftover" fractions of days we need to make up every four years do not add up to precisely one day, a small amount of unnecessary time is added to the calendar. Therefore, a leap day must be skipped to compensate for that time added. This skipped leap day is included during years that are evenly divisible by 100.
    But again, that would not be a perfect solution. We would be taking away a very small amount of time from our calendar. So, there also has to be a leap day on a year evenly divisible by 400, regardless of the "no leap day every 100 years" rule.
Sound complicated?
    In spite of all the confusion, the rules of the leap day can be simplified. There is a leap day every four years, except for every 100 years when there is no leap day. But, there is a leap day every 400 years.
    Contrary to what some people think, the leap day is in fact not a useless day that we add on to February. If we began skipping leap days, then the world would eventually be celebrating New Year’s Day in the summer.

[Sources: news.nationalgeographic.com; www.latimes.com]