Weblog

February 29, 2008

The year 2008 is a leap year. If you look at a 2008 calendar, you will see that February has five Fridays–the month begins and ends on a Friday. Between the years 1904 and 2096, leap years that share the same day of week for each date repeat only every 28 years. The most recent year in which February comprised five Fridays was in and the next occurrence will be in February 29, the leap day has been associated with age-old traditions, superstitions and folklore.

What is a leap year?

A leap year is a year in which one extra day has been inserted, or intercalated, at the end of February. A leap year consists of 366 days, whereas other years, called common years, have 365 days.

Which years are leap years?

In the Gregorian calendar, the calendar used by most modern countries, the following three criteria determine which years will be leap years:

Every year that is divisible by four is a leap year;

Of those years, if it can be divided by 100, it is NOT a leap year, unless

The year is divisible by 400. Then it is a leap year.    

According to the above criteria, that means that years 2000 was somewhat special as it was the first instance when the third criterion was used in most parts of the world
In the Julian calendar–introduced by Julius Caesar in 46 BC and patterned after the Roman calendar–there was only one rule: any year divisible by four would be a leap year. This calendar was used before the Gregorian calendar was adopted.

Why are leap years needed?

Leap years are needed to keep our calendar in alignment with the earth’s revolutions around the sun.

Why the change from the Julian to the Gregorian calendar?

The Julian calendar introduced too many leap days, thus increasing the number of days between the vernal equinox of March 21, its scheduled date as noted in AD 325 during the Council of Nicaea. The introduction of the Gregorian calendar allowed for realignment with the equinox; however, a number of days had to be dropped when the change was made. Click on any one of the year links below for a better explanation of the calendars and the days that were dropped in order to make the switch to the Gregorian calendar.

The Gregorian calendar was first adopted in Italy, Poland, Portugal and Spain in 1582. This was done by dropping 10 days in October of that year.

.In Great Britain (and America), the Gregorian calendar would not be adopted until much later, in September 1752; 11 days were dropped.

Sweden (and Finland) had a “double” leap year in 1712. Two days were added to February–creating a date of February 30, 1712. (This was done because the leap year in 1700 was dropped and Sweden’s calendar was not synchronized with any other calendar. By adding an extra day in 1712, they were back on the Julian calendar.) Read more about February 30

.The Julian calendar is currently (between the years 1901 and 2099) 13 days ahead of the Gregorian calendar (because too many leap years were added).

Other leap years facts

The Gregorian calendar has a 400-year cycle until it repeats the same weekdays for every year–February 29, 2008, is a Friday and February 29, 2408, is a Friday.

The Gregorian calendar has 97 leap years during those 400 years.

The longest time between two leap years is eight years. The last time that occurred was between 1896 and 1904. The next time will be between 2096 and 2104.