Today is 29/02/2008 (A leap year/day)

Leap year

A leap year (or intercalary year) is a year containing one or more extra days (or, in the case of lunisolar calendars, an extra month) in order to keep the calendar year synchronised with the astronomical or seasonal year. For example, in the Gregorian calendar, February would have 29 days in a leap year instead of the usual 28. Because seasons and astronomical events do not repeat at an exact number of full days, a calendar which had the same number of days in each year would, over time, drift with respect to the event it was supposed to track. By occasionally inserting (or intercalating) an additional day or month into the year, the drift can be corrected. A year which is not a leap year is called a common year.

Gregorian calendar
In the Gregorian calendar, the current standard calendar in most of the world, most years whose division by 4 equals an integer are leap years. In one leap year, the month of February has 29 days instead of 28. Adding an extra day to the calendar every four years compensates for the fact that a solar year is almost 6 hours longer than 365 days.

Leap day
Main article: February 29
February 29 is a date that occurs only every four years, and is called leap day. This day is added to the calendar in leap years as a corrective measure, because the earth does not orbit around the sun in precisely 365.000 days.

Birthdays
A person born on February 29 may be called a "leapling". In common years they usually celebrate their birthdays on 28 February or 1 March.

For legal purposes, their legal birthdays depend on how different laws count time intervals. In Taiwan, for example, the legal birthday of a leapling is 28 February in common years, so a Taiwanese leapling born on February 29, 1980 would have legally reached 18 years old on February 28, 1998.

“ If a period fixed by weeks, months, and years does not commence from the beginning of a week, month, or year, it ends with the ending of the day which proceeds the day of the last week, month, or year which corresponds to that on which it began to commence.　 But if there is no corresponding day in the last month, the period ends with the ending of the last day of the last month. ”

In some situations, March 1 is used as the birthday in a non-leap year since it then is the day just after February 28.
(source: www.wikipedia.org)

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A year will be a leap year if it is divisible by 4 but not by 100. If a year is divisible by 4 and by 100, it is not a leap year unless it is also divisible by 400.

Thus years such as 1996, 1992, 1988 and so on are leap years because they are divisible by 4 but not by 100. For century years, the 400 rule is important. Thus, century years 1900, 1800 and 1700 while all still divisible by 4 are also exactly divisible by 100. As they are not further divisible by 400, they are not leap years.
(www.dataip.co.uk/reference/leapyear.php)


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