Name: 什麼是潤年？（What Is a Leap Year?）
Uploaded: 2013-08-15T11:33:12.000Z
Duration: 4 min 1 s
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情態副詞

You probably know that this year, 2012, is a leap year, and that

means that this year we get an extra day on February 29th.

轉承詞

So instead of having 365 days this year there'll be

an extra day--who really cares? Well, people

born on February 29th on some previous leap year, also known as leaplings,

they care because they finally get to celebrate their real birthday.

But for the rest of us it's just a day like any other day--whoop dee doo! So why

One full day is actually how long it takes for the Earth

is how long it takes for the Earth to orbit the sun

In other words, one full year equals 365.25 days.

But here's the problem: Our calendar year is only 365 days,

And so those extra .25 days, they just keep accumulating,

and what they do is make it so that the stars slowly drift out of sync

with our calendar. So this is where Leap Year comes in

Every year we set aside those .25 days, until the fourth year when

they equal one full day. And then on that fourth year we put that extra day on

February 29th and we call it Leap Day. Bam! We're back in sync.

But the real interesting thing is how we humans figured this all out.

It really was the Egyptians who first figured out Leap Year. They noticed by

that the astronomical year was actually 365.25 days, and

But the western world wasn't so fast to figure this all out. It wasn't until many

centuries later when Julius Caesar, with the help of an astronomer, discovered just

like the Egyptians first did that the year is really 365.25

And they created the Julian Calendar with the Leap Year that we know and love

if you want to get really exact about it, the astronomical year is actually

So today, we use a revised version of the Julian Calendar. It's called the

initiated it. The Gregorian Calendar is just like the Julian Calendar, but it's got

So while every fourth year is a leap year, every year that's divisible by

are now no longer leap years. And that means that years 1700, 1800

those were not leap years, even though they normally would be

And here's another rule: If the year is also divisible by 400, then it

And with all those complicated rules, our calendars can stay in sync with the

Did you know that the earth's rotation is slowing at a rate of .005

And that means in about 2 billion years we're gonna have to have to add

we've got plenty of time to revise the calendar and fix that.

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什麼是潤年？（What Is a Leap Year?）

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