why do we have leap year?

Answer 1

The Gregorian calendar, the current standard calendar in most of the world, adds a 29th day to February in all years evenly divisible by 4, except for centennial years (those ending in -00), which receive the extra day only if they are evenly divisible by 400. Thus 1600, 2000 and 2400 are leap years but 1700, 1800, 1900 and 2100 are not.

The reasoning behind this rule is as follows:

The Gregorian calendar is 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 currently about 365.242375 days long.
The Gregorian leap year rule gives an average year length of 365.2425 days.
This difference of a little over 0.0001 days means that in around 8,000 years, the calendar will be about one day behind where it should be. But in 8,000 years' time the length of the vernal equinox year will have changed by an amount which can't be accurately predicted So the Gregorian leap year rule does a good enough job.

Answer 2

Best Answer - Chosen by Asker

A day is the amount of time it takes the earth to rotate 360 degrees. A year is the amount of time it takes for the Earth to travel around the sun, 360 degrees. Since you are using Days as a standard of time measurement, it takes about. 365 and 1/4 day for the earth to take its journey around the sun. Every 4 years a day is added to the year to take into consideration of that 1/4 day. But that is not accurate. There is still error. Every 100 years, the 4th year will not be 366 but 365 days to compensate for the error since it is not exactly 1/4 a day in error. But because there still is an error in the 100 year rule, they have another rule that says every 1000 years, you can go ahead an ignore the 100 year rule and have a leap year.

Our definition of time is based on movement. The movement of the spin of the earth. The movement of the earth around the sun, or the lunar cycle of the moon traveling around the earth. It wasn't until the invention of clocks and other time pieces that allowed us to measure time with a mechanical device that the average person can know the time, but forget the connection

Answer 3

A year is the time it takes the earth to complete one orbit of the sun.
Except that it is not exactly 365 days.
It's about 365 and a quarter days.
So to keep everything in the heavens where it should be, we (usually, there are exceptions to the exception!) add one full day every four years.

The extra day is added to February because it is already the shortest month.

PS: Ha Ha above is not correct. It has nothing to do with the speed of the earth's rotation; that's another matter

Answer 4

I am most likely not accurate... so I am most likely not a good source. I feel that the Earth keeps its own time and for to put organize and track the days moths and years we developed a calender that isn't accurate enough. We loose time each year so to make up for the lost time we have leap years.

Answer 5

Because it doesn't really take exactly 24 hours for the earth to turn. It take like 24.44 or something like that. So, every four years, we put in a new day, and it evens out. Because, if we didn't the days would slowly shift until we'd have winter in July.