What causes the leap year?

Question

I understand that every four year there is a extra day to the year, because a year is 365.25 day. But after a year wouldn't our clocks be six hour off, and after two year it would be 12 hours off, and 18 hours off after three days.? wouldn't our clocks be totally messed up ? please help me

Answer 1

Leap year is one of those things that can really blow your mind if you get to thinking about it too hard.  Let's look at it like this:

Year 1 starts at 12:00 midnight on January 1.  We'll leave an imaginary marker in space where the Earth is at that moment.  The marker isn't going to move, being imaginary and all.

When 12:00 midnight of January 1 of Year 2 rolls around, the Earth hasn't quite returned to that marker; in fact, it won't get there for another six hours.  We should technically wait until about 6 am to sing "Auld Lang Syne", but we have this tradition of starting new days (and new years) at midnight, so we don't.  We just ignore the fact that we were about a quarter day early celebrating Earth's return to the same position in space that we were at at 12:00 on 1/1 of the previous year.  Still with me?  Great!

The next New Years Day rolls around, and the difference between us yelling "Happy New Year" and the Earth returning to its starting point becomes even greater; about half a day.  Technically, the new year shouldn't start until about noon, but, hey...tradition.

You can see where this is heading.  Every year, our celebration of the new year at midnight on January 1st occurs further ahead of the ACTUAL return of the planet to its annual starting point.  We don't really care about the difference until, lo, a whole day has accumulated.  Now, we celebrate the new year at 12:00 midnight of January 1st, when in reality the Earth won't return to the imaginary marker until around midnight of January 2.  If we continue to ignore this discrepancy it's going to build and build and build until our calendar isn't accurate, so...we tack an extra day onto the end of February.  Voila!  Problem solved...when our clocks show 12:00 midnight on January 1st, we will once again be at our imaginary marker.

Or almost.  See, as it turns out, the Earth's year isn't QUITE 6 hours longer than the 365 days we give it.  Every 100 years (on years that end in '00), we have to skip a leap year in order to account for the fact that, by practicing leap years, we're actually getting a bit ahead of the curve.  So that takes care of it, right?

Well...no.  Skipping a leap year every 100 years gets us a little behind again, so on century years that are also divisible by 400 (like the year 2000, for example), we go ahead and have a leap year.  That's why 2000 was a leap year, but 2100, 2200, and 2300 won't be.  2400 will be.

I can hear you saying: Surely with all these fine corrections, the calendar FINALLY reflects real time....right?  Wrong, and don't call me Shirley.  As it turns out, the Earth is making things infinitely more complex by slowing down in its rotation.  That means that every so often we have to adjust our clocks by a second or two.  These "leap seconds" add up over many, many years, so that means that our great-great-great-great-great- (insert many more "greats") grandchildren will have an even more confusing calendar to contend with.

I hope that helps.  Good luck!

(NOTE:  This answer completely ignores the fact that, due to time zone differences, people all over the world are celebrating the new year every hour.  So, technically, somebody ELSE might be celebrating the new year exactly 365.25 days after YOU celebrated it last year.  I'm just talking about the perspective from your own personal time zone).

Answer 2

our clocks are programed to act like there's 365 days per year, and daylight savings helps keep them on time too.

Answer 3

The Earth does a complete orbit around the in approximately 365 days and 6 hours so every four years you build up theose 6 hours into a day!

Answer 4

I'll try to clear this up for you. In the time the it takes the earth to completely revolve around the Sun once, the Earth rotates a total of 365.25 days. So when we celebrate the new year, its not really for another six hours, then twelve, then eighteen. But since our clocks are based on the time it takes the Earth to rotates, not revolve around the Sun, they don't get messed up. Really its just our seasons that are off bye a matter of hours, but the leap year fixes this by making up for four years worth of extra hours and just adding one day to February. I hope this helps...

Answer 5

Its a matter of simple calculation. We do not count the ".25 day".(Remember- we celebrate new year at midnight and not at 6 in the morn.) All these 6 hours add up after four years to produce a day. Thus, a leap year is born. The clock will show 00:00 in the first year, 6:00 in the  second year, and so on. But, we have to change the batteries at least twice a year. Digital clocks are made to compensate with this difference.

Answer 6

The 24 hour time scale is measuring the 1 rotation of the earth

A year is the rotation around the sun.

When the earth hit the same spot in a year of rotating around the sun it is not facing the same direction as it was the last year. If it was nice and neat it would face the same direction every 4 years (But it is not).

Think of it as if a year and a day have nothing to do with each other.

A year is used by humans as a cycle of seasons.

A clock is used to track night and day.

Answer 7

The period of evolution of the earth around the sun, from one point to the same point in its orbit, is 365 days, 5 hours, 48 minutes, and 46.2797 seconds.

This means that in four years time the excess accummulates to about 23.25 hours or almost a day.

To avoid the precession of the seasons, that is the start of spring which corresponds to the vernal equinox in March 22 of each year must remain in March 22, one day is added to the days of the year on the fourth year.. Such years with 366 days are called leap years where the month of February has 29 days instead of the usual 28. Ordinarily years which are multiples of 4 are leap years.

Note however that adding one day every four years overcompensates the four year excess by about 0.74858 and in a period of 100 years the overcompensation amounts to about 18.71445 hours which is almost a day. So every 100th year, no addition is made to 365 days, Thus all centenary years, (Years ening with two zeros), are not leap years although these are multiples of 4, except for the following.

When the 100th year is not made into a leap year, there would be an equivalent undercompensation of 5.28555 hours per century so that in four centuries this excess amounts to 21.1412 hours which is almost one day. So every fourth centenary year is made a leap year although such year is a multiple of 100.

In summary here is how a leap year are accounted:

1. Years which are multiples of 4 are leap years. Except;

2. Centenary Years (Years which end with two zeros), which are not leap years although these are multiples of 4. However;

3. Centenary years which are multiples of 400 are leap years although they end with two zeros.

The clock however is not affected by the leap year compensation as one day is still 24 hours regardless of whether the year is a leap year or not.

Answer 8

I suppose we just agree to accept that phenomenon by convention, knowing we'll make up for it every fourth year.

I guess that, if it comes down to it, you can use this excuse to split hairs with your boss over whether or not you were ACTUALLY at work ON TIME or not!  :)

Answer 9

You're right.  After a year, our clocks ARE 6 hours off, and 12 hours after 2, 18 hours after 3, and a full 24 hours off after 4 years.  So after 4 years we add an extra day in there to make up for that 24 hours.  That's the leap year.

A day (one noon to the next) is still 24 hours, so your watch is always going to tell you it's noon when the sun is high.  The problem is that a year (the time it takes to orbit the sun and come back to our original position) cannot be divided by 24 evenly.  So we have those extra few hours adding up every year, and when they add up to a whole extra day, we throw an extra day in to even everything back out.

Without the leap years, New Years would come at 12AM Jan1 this year, 6AM Jan1 next year, 12PM Jan1 the year after, 6PM Jan1 the next, and starting over at 12AM the next, except this time on Jan2.  Leap year makes up for that day, resetting it at Jan1.

And there's no reason that there SHOULD be an even number of days in a year.  They're two completely different processes, rotation of the earth on its axis giving us days and revolution around the sun giving us years.  Leap years are our way of giving order to that.

Answer 10

Frogs?