From Wikipedia, the free encyclopedia
A leap year (or intercalary year) is a year containing one or more extra days (or, in case of lunisolar calendars, an extra month) in order to keep the calendar year synchronised with the astronomical or seasonal year. For example, February would have 29 days in a leap year instead of the usual 28. Seasons and astronomical events do not repeat at an exact number of full days, so 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.
In the Gregorian calendar, the current standard calendar in most of the world, most years that are divisible by 4 are leap years. In a 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.
However, some exceptions to this rule are required since the duration of a solar year is slightly less than 365।25 days। Years which are divisible by 100 are not leap years, unless they are also divisible by 400, in which case they are leap years.For example, 1600 and 2000 were leap years, but 1700, 1800 and 1900 were not. Going forward, 2100, 2200, 2300, 2500, 2600, 2700, 2900, and 3000 will not be leap years, but 2400 and 2800 will be. By this rule, the average number of days per year will be 365 + 1/4 − 1/100 + 1/400 = 365.2425, which is 365 days, 5 hours, 49 minutes, and 12 seconds.
The Gregorian calendar was designed to keep the vernal equinox on or close to March 21, so that the date of Easter (celebrated on the Sunday after the 14th day of the Moon that falls on or after 21 March) remains correct with respect to the vernal equinox.The vernal equinox year is about 365.242374 days long (and increasing), whereas the average year length of the Gregorian calendar is 365.2425.
The marginal difference of 0।000125 days means that in around 8,000 years, the calendar will be about one day behind where it is now. But in 8,000 years, the length of the vernal equinox year will have changed by an amount which cannot be accurately . Therefore, the current Gregorian calendar suffices for practical purposes, and Herschel's correction (making 4000 AD not a leap year) will probably not be necessary.
In the Hindu calendar, which is a lunisolar calendar, the embolismic month is called adhika maas (extra month)। It is the month in which the sun is in the same sign of the stellar zodiac on two consecutive dark moons। Adhika Maas typically occurs once every 3 years, or 4 times over 11 years. So the yearly lag of a lunar year (which tends to have ten fewer days (355-356 days) per year than solar calendar) is adjusted every 3 years. Thus, Hindu festivals tend to occur within a given span. For example: the No Moon during Diwali festival tends to occur between October 22 and November 15.
लिप दिवस २९ फेब्रुवारी दिनविशेष
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
1896 - Morarji Desai, Prime Minister of India (d. 1995)
अधिक माहिती : http://en.wikipedia.org/wiki/Leap_year#Birthdays