2008 leap year because?
A leap year is whether lasts 366 days, instead of 365 a year together. That extra day is usually added at the end of the month shorter, the date as February 29.
This day is added to correct the gap that exists with the actual duration of the years: 365 days and 6 hours. This makes a correction every four years (years multiples of four) that accumulate 24 hours.
The Julian calendar considered leap years divisible between four. This year Julian lasts 365 days +1 / 4 = 365.25 days (more than a year that lasts tropics 365.2422 days).
The rule for leap years according to the Gregorian calendar is:
A leap year is whether it is divisible by 4, except each of the last century (those divisible by 100), to be leap, also must be divisible by 400.
That means the years that are divisible by 4 are leap, but will not be leap if they are divisible between 100 (as the years 1700, 1800, 1900 and 2100) unless they are divisible by 400 (as the years 1600, 2000 or 2400 ). In 400 years there should be 97 leap years, thus the year of the Gregorian calendar remains very similar to the solar year. So the Gregorian year lasts 365 days +1 / 4 -1/100 +1 / 400 = 365.2425 days (more than a year that lasts tropics 365.2422 days).
Since the error is 0.0003 days per year, it might seem that after three thousand years will have accumulated a day of error. But in reality we do not know exactly when the mistake will come one day. The figure of 365.2422 days per year tropics is not entirely accurate, because both the duration of the year tropics, as the speed of rotation of the earth are changing with the centuries, and in a manner that is not completely predictable.
History of leap year [editing]
Perhaps 365 days with leap years and Gregory XIII reformed so as it is today.
The calendar was the first day of each month. The days preceding the day 1 refers to the calendar of this month. v.g. in a normal year of 365 days: March 1, was the calendar of March, the February 28 was the day before the calendar of March, the February 27th was the 2nd. day before calendar of March (was the day of departure and arrival in the account), on February 26 was the 3rd day before the calendar of March, the February 25th was the 4th day before the calendar of March; February 24 was the 5th day before the calendar of March, the February 23 was the 6th day of the calendar before March. In leap years was added one day after 23, who was a sixth-before the calendar of March. As we no longer have the calendar, we find it more convenient to consider that the day is actually added the last month.