February 29 is an additional extra day on the calendar. Whenever you see this in the calendar, it all means that it’s a Leap Year. So, what exactly is a Leap Year? It is a year that contains extra days for the purpose of keeping the calendar year synchronized with the seasonal year.
Usually, we only have 28 days in the month of February. To synchronize the days of the year, we add one day every Leap Year. To calculate how we can add extra day, it starts to get complicated.
Calculating the Leap Year
The standard calendar that most of the world is using is the Gregorian calendar. With the kind of rule that everybody is using, we can identify that this year is a Leap Year. The standard formula in calculating the Leap Year is that the year must be divisible by four with no remainders on it.
There are exceptions on the rule of calculating the Leap Year. As I said earlier, a year must be dividable by four. If a year is ending with two zeros (-00), which is a centennial year, they must be divisible by four hundred for them to be able to be called a Leap Year. So that means, year 2300, 2200, 2100, 1900, 1800 and 1700 are not included as Leap Years.
Remember that a Gregorian type calendar is intended to retain the vernal equinox, which is composed of about 365.242375 days. This is the reason why a centennial year has an exception because a Gregorian Leap Year gives year duration of about 365.2425 days on the average.
The Rules in Naming the Year as a Leap Year
There are certain kinds of rules to be followed in naming a year as a Leap Year. Before you can add 1 day on the year, you must follow these rules:
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A year can be divided by four.
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If it can be divided by one hundred, it can also be divided by four hundred.
A year is not called a Leap Year if the second rule is not followed. It is called an exceptional common year. Following these rules, number of days on the average will be with the following equation:
365 + (((1/4) – (1/100)) + (1/400))
365 + (((0.25) – (0.01)) + (0.0025))
365 + ((0.24) + (0.0025))
365 + 0.2425 = 365.2425
As year passes, new rules will be implemented for us to identify which is which. After a timescale of ten thousands of years, the number of days in a year will change for some reasons. But for sure, we can’t predict accurately the changes.
Article by TopClock
http://www.topclock.co.uk
Filed under: Clocks, Time keeping | Tagged: calendar calculation, leap year
