When is the next leap year? The answer is the year 2012. To find out if a year is a leap year, simply divide the year by four. If the result is a whole number, that year is a leap year. Take 2012, for example. This number divided by four gives 503. This is a whole number, so 2012 is a leap year. The year 2011, is not a leap year because when 2011 is divided by four, the answer is 502.75, which is not a whole number. The most recent leap years were 2008, 2004, 2000, 1996 and 1992. As you can see, a leap year occurs every four years.

#### Leap Years – A Few Exceptions

♦ There are exceptions to the rule that all years divisible by four are leap years.

♦ The exceptions are some years ending with two zeroes, like 1800, 1900 and 2100. Years that end in two zeroes are not only divided by four; they should also be divisible by 400 to be leap years. Thus, the year 2100, which when divided by 400 gives 5.25 (not a whole number), is not a leap year. But 2000 is, because that number divided by 400 results in a whole number, 5.

#### The Gregorian Calendar

♦ The calendar that is widely used today is called the Gregorian calendar. It has 365 days in a regular year, and 366 days in a leap year. In a leap year, the extra day belongs to February, so there is February 29 in every leap year, and no such date during regular years.

♦ As most people know, a year is (or should be) equivalent to the time it takes the Earth to make one complete revolution around the sun. As such, it is called a solar year. Scientists and astronomers calculate that the actual solar year is 365.2422 days long and this is the exact time it takes the Earth to make a complete revolution around the sun. To reconcile the Gregorian year with a real, solar year, one whole day is added every four years. This makes the leap year.

♦ The addition of one day during a leap year is called intercalation. If it was not done, the Gregorian calendar would be out of sync with a solar year. There would be noticeable disparities in the dates of seasonal events. For instance, the dates that used to mark the start of spring or summer would change. To prevent this from happening, leap years are adopted. They are an effective mechanism to manage the difference between a solar year and a calendar year.

♦ Before the Gregorian calendar, other calendars were used. One example is the Julian calendar, named after Julius Caesar, which was the “official” calendar before the Gregorian calendar replaced it. Today, there are other calendars beside the Gregorian calendar. Chinese calendar is an interesting example of lunar calendar.