The reason for a leap day or a leap year is because our calendar does not follow the Earth's orbit around the sun exactly.

闰日或闰年出现的原因是我们的历法并不精确地遵循地球围绕太阳运行的轨道。

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But one challenge for Apple's sales this year is that its most recent models do not represent a big leap from the previous generation.

但今年苹果在销售方面面临着一个挑战：它最新推出的机型与上一款相比并没有特别大的进步。

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I have written a program to determine whether a year (such as 1900) is a leap year, is the show in 1900 as a leap year, otherwise show that 1900 was not a leap year.

自己编写一段程序判断一个年份(比如1900年)是否是闰年，是则显示1900年为闰年，否则显示1900年不是闰年。

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