Why do we need leap years?

Answer 1

The Earth's rotation is very gradually slowing down.

So, we occasionally add leap seconds to clocks to keep the daily cycle

(as measured by accurate "atomic clocks") as close to the "mean solar day" as possible.

Without leap seconds, "Coordinated Universal Time", based on atomic clocks, would slowly drift farther and farther away from any standard based on the Sun's position in the sky due to Earth's rotation.

The "second" used by atomic clocks was fixed in relation to the Earth's rotation period about a hundred years ago. That's why the two time measurements are now "out of synch". Of course, the gap will continue to grow.

Answer 2

First you must ask yourself what is a day. Is it...24 hours? The time it takes the Earth to spin once completely? Well, bothe of these would wrong. Technically, a day is the time it takes for an object to rotate around its axis. It is different for every planet. For Earth, it is exactly 23 hours, 56 minutes, and 4 seconds. But there are two kinds of days. There is a siderial day, as I explained above, and a solar day. You might be arguing that if it took about 4 minutes less than 24 for a day, how come the Sun is always overhead at noon, out of sight at night? When we take the Sun into account (and that the Earth is revolving around it), it's a different story. Check out my diagram (as best I can make it) below. Suppose this is the very beginning of the day. Note that the 'E' in EARTH is facing direnctly at the SUN. ............................SUN........................................EARTH 23 hours, 56 minutes and 4 seconds later, the Earth makes one full rotation. But it also travels slightly around the Sun. Here is what it looks like now: ............................SUN ....................................................................... EARTH This is exaggerated, but is true to make a point. Notice how the `E`in EARTH is no longer facing exactly at the Sun? The Earth needs to turn a little more...exactly 3 minutes and 56 seconds worth of turning, making the solar day exactly 24 hours long. But a year is the time it take for the Earth to revolve around the Sun. Counting a day as 23 hours 56 minutes and 4 seconds, this takes exacty 365 days, But when you use the regular calendar, this will have to add up to more - so to make our calendar in sync with the revolution of the Earth around the Sun we have to have leap years. The rule for when a leap year is: A leap year is a day added in February (29th) that falls in a year divisible by 4, but if it is also divisible by 100 then it must also be divisible by 400 to be a leap year. This means 2000, 2004, 1904, 1600, and on and on were leap years, but 1900, 1800, 1700 were not.
You have to have leap year because the Earth doesn't go around the sun in EXACTLY 365 days. It goes around in 365.256366 days or 1.0000175 years. All those .256366 days add up. You have to do something with them or else you'll eventually end up with Christmas in July. So you have leap year. You NEED to have leap year ...so everything can happen at the same time every year.

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You don't NEED to have leap years; you can have any kind of "year" that you want. And if you lived in the tropics, where there aren't any real seasons, some cultures do just that. But because the rate at which our Earth spins isn't exactly divisible into the rate at which the Earth goes around the Sun, you will probably want to have some method of keeping the printed calendar on the wall at least somewhat synchronized to the seasons. Hence, leap years.

Not all cultures do leap years, and the ones that do don't all figure them the same way. The lunar Islamic calendar has no leap years, and the holidays float from season to season. A particular holiday like Ramadan can be in the fall one year and in the winter a few years later; it isn't synchronized at all with the solar calendar. The Jewish calendar is also lunar, but adds a "leap month" every few years so that Passover is always in the spring, and Rosh Hashana is always in the early fall.

Answer 3

It's a bit complicated, but the basic reason is that the Earth's rotation is slowing down gradually.

The leap seconds are added because it makes time measured by accurate clocks keep "in synch" with the time as measured by the Earth' rotation.

Without the leap second, in a couple of hundred years, our time might be off by a couple of hours. Eventually, day time would be nighttime according to clocks that hadn't been adjusted with leap seconds.

Answer 4

Every four years there is a leap year. Instead of 365 days it is 366 days. On a common year it is a February 28th and on leap years it is February 29th. If we don't have leap years every four years, this would happen. Lets say 30 years from today Christmas would be in the summer and it wont be good, because Christmas is one of our favorite holidays and it needs to be in December.

Answer 5

The Earth orbits one time around the Sun in 365.24 days. If we intend that our calendar stay synchronized with the solar year and with our seasons, we need to adjust the calendar periodically.

The Gregorian calendar, the one commonly used by America and Europe, adjusts the calendar by adding an extra day every four years. Leap years occur every four years, except that century years (divisible by 100) are NOT leap years UNLESS they are also divisible by 400, in which case they ARE leap years. So 1900 was not a leap year, while 2000 was and 2100 will not be a leap year.

The Hebrew calendar is primarily lunar; the month begins at the "new moon". In order to keep the calendar somewhat synchronized to the solar year and to the seasons, leap MONTHS are added periodically. This keeps Jewish holidays in the same seasons each year.

Some lunar calendars, such as the Islamic calendar, are not synchronized to the solar year at all. In this case, Islamic holidays occur in different seasons every few years.

Answer 6

We need leap years to account for the fact that it takes the Earth approximately 365.25 days to orbit the sun. Without adding an extra day every four years, the calendar would gradually fall out of sync with the seasons. Leap years help us keep our calendars aligned with the Earth's orbit.

Answer 7

bcos the earths rotation is slowing down really slowly

Answer 8

a leap year is a year which has another day in it (366 instread of 365). it occurs becasue it takes 365.25 days to go around the sun

Answer 9

because Every year is 365 1/4 days. The 1/4 part adds up to a whole day every four years. Because of this, there is an extra day in a leap year. The extra day, called Leap Day, is on Feb 29.